Learning purpose

This lesson examines three separate requirements which determine whether a construction promise creates an enforceable contractual obligation. Consideration asks whether the promise forms part of a legally recognised exchange. Intention asks whether the parties objectively meant their arrangement to affect their legal rights. Certainty asks whether the court can identify the obligation which each party undertook. A claim for an acceleration payment may fail under any one of those requirements even where additional labour was deployed and both parties expected earlier completion.

Successful completion requires the learner to identify the consideration supporting an original promise or contractual variation; distinguish an existing duty from additional performance and practical benefit; determine whether commercial communications reveal present contractual intention; separate an immediately binding agreement from negotiations subject to approval or formal execution; test price, time and performance provisions for certainty; explain when interpretation, implication or an objective valuation mechanism can resolve an apparent omission; and prepare a reasoned opinion from a project record containing instructions, qualifications, performance and unresolved commercial terms.

1. Consideration and the contractual exchange

Consideration is the legal requirement that a promise made by simple contract must form part of an exchange recognised by law. The doctrine does not ask whether the bargain was commercially wise, economically equal or fairly priced. It asks whether the promisee gave, promised or refrained from something in return for the promisor's commitment. A bilateral construction contract ordinarily supplies consideration through the exchange of promises: the contractor promises to carry out the works, while the employer promises payment and the performance of its corresponding obligations. Once performance begins, the acts undertaken discharge obligations created by that earlier exchange.

The inquiry must identify the particular promise which the claimant seeks to enforce. Consideration supporting the original building contract does not automatically support every later promise to pay more money, extend time, release liability or alter the scope. A contractual variation is itself an agreement and ordinarily requires its own consideration unless executed as a deed or governed by another legally sufficient route. Claims specialists should therefore state the alleged variation, identify what each party promised under it, and compare those promises with the duties already owed under the existing contract.

Consideration must move from the promisee, although it need not move to the promisor personally. The claimant must show that it supplied the requested act, promise or forbearance which supported the defendant's commitment. Performance supplied by an unrelated third party will not ordinarily support the claimant's enforcement of a promise unless the contractual structure gives that performance the required legal connection. Within a project group, the fact that one company funded an acceleration measure does not establish that another company supplied consideration for the employer's payment promise. The contracting entities and the direction of each promise must be recorded accurately.

English law does not ordinarily measure whether the consideration supplied was economically adequate for the promise obtained. A court does not reprice a freely negotiated subcontract merely because one party made a poor bargain or because the exchange later appears unequal. The distinction between adequacy and sufficiency prevents a value judgment from replacing the parties' bargain while preserving the requirement for something which the law recognises as consideration. In Chappell & Co Ltd v Nestlé Co Ltd [1959] UKHL 1; [1960] AC 87, the required chocolate wrappers formed part of the stipulated exchange even though their economic value was negligible after receipt. Construction analysis should therefore ask what was bargained for, rather than whether the additional payment matched the contractor's cost.

The timing of the exchange also matters because an act completed before the promise was made will not ordinarily constitute consideration for that later promise. If a subcontractor completes weekend working and the contractor subsequently promises an additional payment as a reward, the completed work was not undertaken in exchange for that later promise. The exception explained in Pao On v Lau Yiu Long [1979] UKPC 17; [1980] AC 614 requires the earlier act to have been performed at the promisor's request, the parties to have understood that payment or another benefit would follow, and that benefit to have been legally enforceable if promised before performance. That chronology must establish all three conditions, together with the later promise which fixes or confirms the anticipated remuneration, without treating gratitude as bargain.

An existing contractual duty creates a harder question concerning whether the later exchange supplies anything legally new. The traditional rule associated with Stilk v Myrick (1809) 2 Camp 317 is that a promise to perform no more than an obligation already owed to the same promisor does not, without something further, supply consideration for an additional payment. Applied mechanically, the rule would prevent a contractor from enforcing extra payment merely for promising to complete the work which it was already bound to deliver. The rule protects against a party extracting a higher price by threatening non-performance while supplying nothing beyond its existing bargain.

Construction variations often contain performance which is genuinely additional and therefore avoid the existing-duty problem. An employer may require an earlier completion date, extended working hours, resequencing, additional supervision, altered access arrangements or procurement from a faster supplier. If the original contract required completion by 30 November and the contractor promises completion by 11 October, that earlier obligation is capable of constituting fresh consideration. The opinion should identify the additional legal obligation itself rather than rely only upon the cost or inconvenience associated with performance.

An acceleration proposal may combine additional duties with work which the original contract already required the contractor to perform. The contractor might promise a second shift and revised sequence but retain the original completion date, leaving uncertainty about whether the employer purchased a defined new obligation or merely received a plan for performing the existing one. Additional expenditure does not by itself prove additional consideration because a contractor may choose a more expensive method to discharge an unchanged duty. The exchange must be found in what the contractor promised the employer, not merely in the contractor's internal resource decision.

Williams v Roffey Bros & Nicholls (Contractors) Ltd [1989] EWCA Civ 5; [1991] 1 QB 1 establishes that practical benefit may provide consideration for a promise to pay more where the promisee continues performance of an existing duty. The main contractor expected advantages from the carpenter's continued work, including reduced exposure to delay and avoidance of the trouble and expense associated with replacement labour. Accordingly, the Court of Appeal held that the practical benefit was capable of supporting the promise of additional payment, provided the promise was not procured through economic duress or fraud.

The practical-benefit analysis does not abolish consideration or convert every commercial advantage into an enforceable variation. Enforceability therefore requires the promisor to obtain a benefit or avoid a disbenefit in practice as a result of the promise sought, and the agreement must remain free from illegitimate pressure. A vague hope that performance will improve does not identify the exchange. The claims specialist should specify the expected benefit, connect it with the requested promise, identify the evidence available when the promise was made, and examine whether the promisee threatened a breach to obtain the additional payment.

Economic duress remains legally separate from consideration, although the facts supporting the two analyses may overlap considerably. A contractor may provide consideration while obtaining the employer's promise through pressure which the law treats as illegitimate. Conversely, hard commercial negotiation does not become duress merely because the employer had little time and strong reasons to secure acceleration. In Pakistan International Airline Corporation v Times Travel (UK) Ltd [2021] UKSC 40, the Supreme Court identified an illegitimate threat or pressure, sufficient causation and the absence of a reasonable alternative as the required elements, while explaining that lawful-act economic duress will arise only rarely in commercial negotiation. The opinion should examine the nature of any threatened conduct, whether the contractor asserted a lawful entitlement, the alternatives realistically available, the protest made and the speed with which the employer sought to avoid the agreement. Consideration's existence should not be used as a substitute for that separate factual and legal inquiry.

The doctrine must also distinguish promises to pay more from promises to accept less. In Rock Advertising Ltd v MWB Business Exchange Centres Ltd [2018] UKSC 24, the Supreme Court decided the appeal under a no-oral-modification clause and deliberately left the consideration issue unresolved. Lord Sumption explained that applying practical benefit to an agreement accepting less or later payment would require examination of Foakes v Beer (1884) 9 App Cas 605. A construction opinion should not state that Williams v Roffey Bros automatically validates every revised payment arrangement.

Part-payment, compromise and release therefore require careful classification before any conclusion concerning consideration can properly be reached. An employer promising additional money for earlier completion presents a different question from a contractor accepting less than a certified debt, or an employer agreeing to release a liquidated-damages claim in return for prompt payment. The legal value may lie in accelerated performance, compromise of a genuinely disputed claim, mutual releases, provision of security or another requested promise. Any opinion must identify that element expressly instead of describing the arrangement as commercially beneficial in general terms.

Consideration should finally be separated from evidence of performance and from quantum. Timesheets, revised programmes and delivery records may prove that acceleration measures occurred, but they do not alone establish the exchange which made an additional-payment promise binding. Cost records may prove expenditure while leaving the agreed valuation basis uncertain. The formation analysis should identify the promises first; the performance records should then show whether those promises were carried out; and the valuation analysis should determine the amount payable under the agreed mechanism.

2. Intention to create or vary legal relations

Contractual intention concerns whether the parties objectively meant their agreement to create, alter or extinguish legal rights. It does not require evidence that the participants used the phrase "legally binding" or privately understood every legal consequence. The court considers the communications and conduct within the commercial setting in which the alleged agreement was made. Wells v Devani [2019] UKSC 4 and RTS Flexible Systems Ltd v Molkerei Alois Müller GmbH & Co KG [2010] UKSC 14 require an objective assessment of what the parties conveyed, rather than an inquiry into undisclosed reservations or later recollections of subjective intention.

Commercial construction dealings ordinarily provide a strong setting for contractual intention because price, programme and risk are negotiated between businesses performing an economic transaction. That commercial setting is not conclusive where the parties' communications objectively preserve a condition upon legal commitment. The language may demonstrate that the parties intended no immediate legal commitment, perhaps because the arrangement remained "subject to contract", "subject to board approval", "for discussion only" or conditional upon execution of a formal instrument. A sound conclusion must account for the words which qualify commitment rather than rely upon a general commercial presumption.

Intention must be examined in relation to the particular arrangement which the claimant alleges created or varied contractual obligations. The parties may intend their original construction contract to bind while treating an acceleration proposal as non-binding negotiation. They may create a limited early-works agreement without intending the full amended programme and price to become effective. Those parties may agree an operative instruction while reserving valuation for determination under the existing contract. A general statement that the parties were in contractual relations does not answer whether the later promise altered those relations.

The distinction between present commitment and future agreement is central to any analysis of an alleged acceleration variation. A statement that the employer "will consider an additional payment after completion" ordinarily records a future decision rather than a present promise. Language stating that the employer "agrees to pay the contractor's demonstrable acceleration cost, to be assessed under clause 12" may create an immediate obligation despite postponing calculation. The opinion should identify whether anything remained subject to further consent or whether only measurement, certification or documentation remained outstanding.

Approval conditions require exact treatment because they may postpone commitment even after the substantive commercial provisions have been negotiated. A project manager may state that a price is agreed "subject to board approval", which ordinarily indicates that approval remains a condition of commitment rather than an internal formality already satisfied. Another communication may state that the project manager has authority and that board ratification will follow for governance purposes, which presents a different objective message. Evidence of delegated authority cannot remove an express condition if the communication itself makes commitment dependent upon the later approval.

The intention inquiry also addresses whether formal execution was agreed as a condition of contractual effectiveness. Parties may intend that no variation becomes effective until signed by named representatives, or they may use signature only as evidence of an agreement already made. Rock Advertising confirms that a no-oral-modification clause can prevent an informal variation even where the parties orally agreed its substantive terms. Claims specialists must therefore examine the existing contract's variation formalities before concluding that an acceleration instruction and response formed an effective amendment.

No-oral-modification provisions serve evidential and organisational purposes within construction businesses operating through numerous technical and commercial representatives. They reduce disputes about informal site conversations, preserve internal authority controls and direct changes into a recorded process. Their operation can produce a hard result where a contractor performs an orally agreed acceleration measure and later discovers that the stipulated writing and signature were absent. The factual analysis must identify any compliant variation, any separate written agreement, and any unequivocal representation and reliance capable of supporting an estoppel argument without assuming that performance alone removes the clause.

"Subject to contract" wording ordinarily maintains a negotiating reservation until the parties execute the intended instrument or clearly abandon the qualification. Lord Briggs addressed the analogy in Rock Advertising, explaining why full agreement upon substantive terms does not alone remove a formal reservation. Construction correspondence may use less established expressions such as "commercials to follow", "without prejudice to final agreement" or "pending formal instruction". Their effect depends upon objective construction, but each warns against treating mobilisation as proof of immediate assent to every proposed term.

Conduct remains relevant because parties sometimes communicate intention more clearly through contractual administration than through incomplete drafting. Issuing a formal instruction, approving a revised programme, certifying a separate acceleration amount and applying an agreed valuation method may support present legal intention. The same work may remain equivocal where the contractor was already obliged to mitigate delay, where an emergency instruction operated under existing terms, or where both parties repeatedly recorded that price and target awaited approval. Conduct must be linked to the alleged variation rather than described at a high level.

Performance on both sides may make denial of contractual intention difficult where the acts objectively implement the alleged agreement. RTS Flexible Systems explains that an executed or partly executed transaction may reveal an agreement which the documents alone do not present neatly. The court may find that matters left open during negotiation were not conditions of commitment or were capable of objective resolution. That approach does not authorise the court to disregard express reservations which remained operative throughout the relevant performance. Extensive performance assists only where it objectively demonstrates the legal relationship which the parties chose.

The identity and authority of the participants form part of the intention analysis. A planner may agree a technical acceleration sequence without authority to promise payment, while a commercial director may agree price but reserve approval of a revised completion date. The employer's objective intention is assessed through authorised communications and any applicable agency principles. In The Law Debenture Trust Corporation plc v Ukraine [2023] UKSC 11, the Supreme Court explained that apparent authority rests upon a representation attributable to the principal upon which the contractor reasonably relied. A contractor cannot invoke the doctrine where the circumstances required reasonable inquiry into authority and the contractor failed to make that inquiry. An express approval limit known to the contractor may therefore prevent reliance upon apparent authority.

Intention is also relevant to comfort letters, meeting records and statements of principle. A minute stating that "the parties agree in principle to develop an acceleration arrangement" may record consensus about a commercial objective without creating the final variation. By contrast, a signed record stating that "the contractor shall complete by 11 October and the employer shall pay demonstrable acceleration costs up to GBP 600,000" has a different objective character. Labels are not decisive, although language of principle, draft status and future documentation may reveal that commitment remains incomplete.

Claims submissions often confuse reliance with contractual intention, although those concepts perform different legal and evidential functions. A contractor may act upon an employer's assurance and incur substantial cost, which strengthens the factual case that the assurance was treated seriously. Reliance does not by itself prove that the assurance was intended as a contractual promise, nor does it necessarily satisfy agreed formalities. The analysis may require consideration of estoppel or restitution, but those doctrines should not be used to conceal a failure to identify the alleged contract or variation.

A final intention conclusion should specify the date and legal scope of any commitment. It should state whether the parties intended an immediately binding acceleration variation, a limited instruction valued under the existing contract, a conditional agreement awaiting approval, or a non-binding negotiation. That assessment should then identify the communications and conduct which support that classification, together with any formal requirement or authority issue capable of defeating it.

3. Certainty and completeness of the bargain

Certainty requires the alleged agreement to contain, or provide an objective means of identifying, the obligations which the law treats as necessary for enforcement. The doctrine does not demand perfect drafting or an express answer to every future contingency. Commercial contracts frequently leave matters to measurement, certification, implication or legal standards. The question is whether the court can ascertain the bargain made without constructing a bargain which the parties never reached.

Required certainty depends upon the transaction, the term in issue and its contractual context. A sale may require an identifiable subject matter and price or price mechanism, while an acceleration variation may require a defined performance obligation, temporal target and payment basis. If the employer promises "something extra" for finishing "as soon as possible", the court may be unable to determine either side of the exchange. Where the employer promises reasonable demonstrable cost for specified measures intended to achieve a dated milestone, the valuation can remain open while the obligation is objectively workable.

Price certainty does not always require a fixed numerical amount to appear within the communication forming the alleged agreement. The contract may provide rates, cost reimbursement, a formula, independent certification, reasonable price or another objective mechanism. A controlling distinction lies between an incomplete agreement requiring a future bargain and an operative agreement requiring a later calculation. Language promising "an amount to be agreed" commonly leaves consent outstanding between the parties. By contrast, a promise to pay "the contractor's verified additional labour and plant cost, assessed by the quantity surveyor under Schedule 4" supplies an external standard and machinery.

Time obligations require the same analytical discipline applied to price, scope and the conditions governing contractual commitment. "Accelerate the works" may identify a method but not the result purchased. "Complete earlier" leaves the temporal obligation undefined unless the surrounding communications establish a date or measurable period. A dated sectional milestone, reduction of six weeks, or approved revised programme can provide the required standard. Where several programmes circulate, the opinion must identify the version incorporated and whether it was accepted as contractual or issued only for monitoring.

Scope certainty matters because the contractor's acceleration measures may apply to only part of the works. A promise concerning facade closure cannot automatically be treated as an obligation to achieve practical completion of the entire project. The record should identify the affected activities, interfaces, access assumptions, design releases and employer dependencies. An apparently precise date may remain unworkable if the parties did not identify the work to which it applies or the conditions upon which achievement depends.

Wells v Devani demonstrates the court's approach to a bargain which omits an expressly discussed payment trigger. The Supreme Court examined the words and conduct in context and held that the parties had made a binding agreement under which commission became payable when the introduced purchaser completed. That decision distinguishes interpretation of the bargain from implication of a term after formation. It also confirms that the court cannot enforce words and conduct which remain too vague to disclose contractual intention or terms.

The judicial reluctance to defeat an intended bargain becomes stronger where the parties acted upon it. Performance may show which meaning the parties gave an expression, whether an apparently open matter was treated as inessential, or whether an objective valuation method was understood. RTS Flexible Systems treats performance as relevant to formation and completeness, particularly where the parties carried out a substantial commercial transaction. The court nevertheless refused to adopt a rule that performance always creates the contract under negotiation.

Scammell v Ouston [1941] AC 251 illustrates the opposite result where the missing structure could not be objectively ascertained. The agreement referred to hire-purchase terms without identifying which of several materially different arrangements applied. Consequently, the House of Lords could not supply the missing financial structure and held the agreement unenforceable. In a construction setting, a reference to payment "under the usual acceleration arrangement" may present the same problem where the parties have no established form, course of dealing or incorporated mechanism.

An agreement to negotiate or agree a material term later presents another boundary. Courtney & Fairbairn Ltd v Tolaini Bros (Hotels) Ltd [1975] 1 WLR 297 concerned a proposed construction arrangement under which remuneration remained subject to later agreement. The Court of Appeal would not enforce an agreement to negotiate the contract price. That authority does not prevent enforcement of a price fixed by an objective standard; it prevents the court from replacing a future consensual bargain which the parties reserved to themselves.

Modern decisions continue to examine the precise obligation rather than apply a slogan about agreements to agree. In Emirates Trading Agency LLC v Prime Mineral Exports Private Ltd [2014] EWHC 2104 (Comm), the Commercial Court distinguished an open-ended negotiation from a time-limited dispute-resolution obligation within an existing contract. The decision shows why certainty depends upon defined process, duration and subject matter. A construction clause requiring named representatives to meet within ten working days and refer unresolved valuation to adjudication differs from a promise that the parties will agree a fair price later.

An objective standard does not make every uncertain promise enforceable where essential elements of the proposed exchange remain unresolved. "Reasonable cost" may be workable where the work, cost categories, records and assessment method are identifiable. "Fair compensation" may remain uncertain where the communication leaves scope, risk allocation and valuation entirely open. The opinion should identify the legal or contractual standard available to control the decision. It should not assume that inserting the adjective "reasonable" supplies all missing terms.

Certainty must be assessed across the complete contractual structure rather than confined to the alleged variation document in isolation. An acceleration letter may omit valuation details because the existing variation clause supplies them. Another letter may attempt to create a separate lump-sum bargain and expressly exclude the existing mechanism, leaving no objective price route. Incorporation, order of precedence and continued operation of the original terms must therefore be resolved before declaring the variation incomplete.

Conditions and assumptions also affect completeness because qualified assent may reveal continuing disagreement rather than an uncertain concluded bargain. A contractor may price acceleration on the basis of unrestricted weekend access, design release by specified dates and no further scope change. If the employer accepts the price but does not accept those assumptions, the parties may lack matching assent rather than merely face uncertain performance. The analyst should separate uncertainty within an agreed obligation from continuing disagreement about the obligation itself.

Available judicial techniques for resolving apparent omissions have defined limits which protect the boundary between adjudication and negotiation. Interpretation can identify the objective meaning of the parties' words and conduct. Implication can supply a term where the legal test is met within an existing agreement. A statutory or contractual rule may provide a reasonable price or time. None of those techniques permits the court to invent a target, choose a commercial cap, allocate an unagreed delay risk or decide which proposed bargain would have been sensible.

The certainty conclusion should address each obligation separately before determining whether those obligations together form an enforceable acceleration bargain. Price may be sufficiently certain while the completion target remains open, or the target may be fixed while the valuation machinery remains subject to agreement. Certainty concerning only part of the proposed arrangement does not necessarily produce a contract whose provisions can be severed. The opinion should state whether the enforceable provisions can operate independently, whether the unresolved matter was a condition of commitment, and whether the project conduct supplies objective evidence without contradicting an express reservation.

4. Judicial analysis

4.1 Williams v Roffey Bros: additional payment and practical benefit

In Williams v Roffey Bros & Nicholls (Contractors) Ltd [1989] EWCA Civ 5; [1991] 1 QB 1, the defendants held the main contract for refurbishment of a block containing twenty-seven flats. They subcontracted the carpentry work to Mr Williams for GBP 20,000. The agreed price proved too low for satisfactory and profitable performance, progress deteriorated, and the main contractor faced delay consequences under its employer contract.

Later, the parties agreed an additional payment of GBP 10,300, calculated at GBP 575 for each flat completed. The promise sought continued and timely performance of work already required under the subcontract. Accordingly, the legal issue was whether Mr Williams supplied consideration for the additional payment despite promising performance of his existing contractual duty.

Glidewell LJ formulated a practical-benefit analysis for a promise to pay more. Where the promisor doubts whether the promisee will complete, promises additional payment for timely performance, obtains a practical benefit or avoids a disbenefit, and gives the promise without economic duress or fraud, that benefit is capable of constituting consideration. The Court of Appeal held that the main contractor obtained practical advantages from continued performance and that the additional-payment promise was enforceable.

Importantly, the decision did not hold that the subcontractor's financial difficulty automatically created consideration. The main contractor obtained the benefits which it sought through the new arrangement, and the payment structure identified the additional amount attributable to completed flats. There was no finding that either fraud or economic duress had procured the additional-payment promise from the main contractor. Those elements must be proved from the project record rather than assumed whenever a contractor requests financial assistance.

For acceleration claims, the first question remains whether the contractor promised an additional obligation, such as earlier completion or defined additional measures. If it did, consideration may be established without relying upon practical benefit. Where the contractor promised only its existing performance, Williams v Roffey Bros requires identification of the benefit obtained and examination of pressure. The authority should not be cited as a substitute for analysing the actual variation.

4.2 Wells v Devani: certainty derived from the objective bargain

In Wells v Devani [2019] UKSC 4, the trial judge found that Mr Devani explained his commission rate during a telephone conversation and later introduced the purchaser which completed the acquisition. The parties did not expressly discuss the event which would trigger the commission. Mr Wells argued that the missing trigger prevented a complete and enforceable contract.

Lord Kitchin held that formation required objective assessment of the parties' words and conduct, their intention to create legal relations and the terms required for a binding agreement. The court was entitled to interpret the exchange within the factual and commercial setting disclosed by the evidence. It was naturally understood that commission would become due upon completion and would be paid from the sale proceeds.

Lord Briggs agreed that the agreement was sufficiently complete when construed through the words, conduct and context. His reasoning distinguishes interpretation from an attempt to repair an agreement through implication after finding that an essential matter was never agreed. The transaction disclosed the service promised, the commission rate, the contemplated sale and the event which objectively connected performance with payment.

Any construction analogy must be applied with restraint because acceleration negotiations may leave several materially different commercial outcomes available. A court may identify a price trigger or valuation route which the accepted words and context already convey. It cannot select one of several disputed completion dates, decide an unagreed acceleration price or impose a programme which neither party accepted. Wells v Devani supports enforcement of the bargain objectively made, not completion of an unfinished negotiation.

4.3 RTS Flexible Systems: intention, performance and incomplete formality

In RTS Flexible Systems Ltd v Molkerei Alois Müller GmbH & Co KG [2010] UKSC 14, the parties began work under a limited letter of intent and continued negotiating a wider contract. They later performed, paid and agreed a programme variation without executing the contemplated formal instrument. The Supreme Court examined the complete communications and conduct to decide whether a wider contract existed and upon which terms.

At paragraph 45, Lord Clarke stated the objective formation test which governs intention and certainty. The court considers what the parties communicated, whether they intended legal relations and whether they agreed the terms which they treated, or the law treats, as required. Terms of economic consequence may remain unfinished without preventing formation if the objective record shows that the parties did not make them conditions of commitment.

The transaction's performance assisted the court because the parties had operated an extensive commercial arrangement and implemented agreed terms. Ultimately, the court held that they formed the wider contract and waived the execution condition through unequivocal conduct. That result depended upon the detailed history, including the matters settled by 5 July and the agreed variation on 25 August.

An acceleration arrangement may similarly emerge through instruction, revised programme, performance, certification and payment. The analysis must still identify the terms implemented and any express reservation which remained operative. RTS Flexible Systems does not permit extensive work to erase a recorded statement that no acceleration price or target will bind until board approval.

4.4 Rock Advertising: agreed formality and unresolved consideration

In Rock Advertising Ltd v MWB Business Exchange Centres Ltd [2018] UKSC 24, a licence required contractual variations to be recorded in writing and signed. The parties orally discussed and, on the trial judge's finding, agreed a revised payment schedule. Accordingly, the Supreme Court held that the no-oral-modification clause prevented the oral variation from taking effect.

Lord Sumption identified legitimate commercial functions for the clause, including prevention of informal attempts to undermine the written agreement, reduction of disputes about the terms of variations and enforcement of internal authority controls. The decision requires construction practitioners to examine the agreed variation procedure before treating oral instructions or meeting exchanges as effective amendments.

However, the Supreme Court did not decide whether the revised payment arrangement was supported by consideration. At paragraph 18, Lord Sumption explained the tension between practical benefit under Williams v Roffey Bros and the rule governing acceptance of less under Foakes v Beer. The issue was unnecessary once the agreed formality disposed of the appeal.

For acceleration claims, the lesson concerns contractual procedure as well as the substantive terms of the alleged exchange. Consideration, intention and certainty may all exist while the variation remains ineffective because the agreed writing or signature condition was not satisfied. Estoppel may require separate analysis, but the informal promise alone cannot destroy the protection which the formal clause was intended to provide.

4.5 Supporting certainty and intention authorities

Scammell v Ouston [1941] AC 251 concerned an agreement referring to hire-purchase terms without identifying the applicable financial arrangement. The House of Lords held that the court could not determine which materially different terms governed. Accordingly, the case demonstrates that an apparent agreement fails where the missing structure cannot be found through interpretation or an objective mechanism.

Similarly, in Courtney & Fairbairn Ltd v Tolaini Bros (Hotels) Ltd [1975] 1 WLR 297, a proposed construction arrangement left remuneration to future negotiation. The Court of Appeal refused to enforce the promise to negotiate and agree the price. A construction record stating that "commercials will be agreed later" should therefore be treated differently from an operative instruction valued under existing rates or a defined reasonable-cost mechanism.

In Ganz v Petronz FZE [2024] EWHC 635 (Comm), the Commercial Court applied the objective formation test and examined whether the payments relied upon were performance of the alleged agreement. The court referred to the RTS Flexible Systems principle that performance on both sides may make denial of contractual intention unrealistic, but found that the payments were not advances under the alleged agreement and that the principle therefore had no force upon the facts. Ultimately, the claimant's case failed because the evidence did not establish an authentic and binding agreement.

These authorities establish a controlled approach to determining whether an apparently incomplete commercial arrangement can be enforced. The court seeks the agreement objectively disclosed, gives weight to commercial performance, and uses available mechanisms to resolve apparent gaps. It will not transform an agreement to negotiate into a completed bargain or treat expenditure as proof of contractual intention without examining the basis upon which it was incurred.

5. Method of analysis for an acceleration promise

The review should begin with a variation chronology linked to the existing contractual obligations. Each entry should record the communication or act, its author and recipient, the authority of both participants, the promise allegedly made by each party, every condition or qualification, the applicable contractual formality and the performance which followed. The chronology should separate technical acceleration discussions from communications alleged to contain a present commercial and contractual commitment.

Stage one identifies the original duties against which any alleged fresh promise or practical benefit must be tested. The reviewer should extract the contractual completion date, sectional milestones, programme obligations, mitigation duties, variation powers, valuation rules, notice provisions and no-oral-modification clause. Without that baseline, the opinion cannot determine whether the contractor promised additional performance or merely adopted a different method of satisfying an existing obligation.

The second stage states the alleged variation precisely enough to identify the performance and payment obligations said to have changed. A conclusion that the employer "agreed acceleration" is insufficient because acceleration may describe resources, sequence, a dated result or an aspiration. The working proposition should identify the revised completion obligation, the measures promised, the price or valuation mechanism, the employer dependencies, the risk assumptions and the date upon which the alleged agreement took effect.

Stage three maps consideration in both directions and distinguishes each new promise from the obligations already contained in the contract. The contractor's consideration may consist of an earlier completion date, additional shifts, resequencing, procurement commitments or relinquishment of an arguable entitlement. Employer consideration may consist of additional payment, altered access, release of liability or another promised performance. If the contractor supplied only an existing duty, the note should identify the practical benefit relied upon under Williams v Roffey Bros and examine duress.

The fourth stage determines objective intention by examining every material communication within its contractual and commercial setting. At this stage, the reviewer should distinguish language of present commitment from provisional approval, future consideration and agreement in principle. Every expression such as "subject to contract", "subject to board approval", "commercials to follow", "without commitment" or "pending formal instruction" should be preserved in the chronology. Later conduct must then be tested against those reservations and the legal basis upon which performance might otherwise have occurred.

The fifth stage tests certainty term by term before considering whether the provisions together establish a workable contractual arrangement. Each target date, affected work, acceleration measures, payment amount, valuation basis, cap, records, access assumptions and treatment of employer delay should each receive a separate conclusion. The note should identify whether an omitted matter is supplied by the existing contract, objective calculation, legal implication or accepted project record. A matter expressly reserved for future agreement should not be recast as an objective calculation merely to preserve the alleged bargain.

The sixth stage addresses formality and authority as requirements distinct from consideration, intention and substantive certainty. At stage six, the claims specialist should compare the alleged variation with the contract's requirements for writing, signature, named approval and document format. Evidence of authority should be obtained for every person said to have committed the organisation. Where the requirements were not met, the reviewer should consider whether a compliant later document, separate contract or properly supported estoppel argument exists.

The seventh stage examines performance as evidence without treating expenditure or completed work as conclusive proof of formation. Labour returns, plant allocation, revised programmes, access records, design releases, meeting minutes, certificates and payments may establish what occurred and why. The opinion should explain whether that conduct is referable to the alleged acceleration agreement, an existing mitigation obligation, an instructed variation under the original contract or work undertaken at the contractor's risk.

Stage eight fixes the legal and financial consequence supported by the completed formation, performance and valuation analyses. The conclusion should state whether there was an enforceable variation, a limited instructed change valued under the original contract, a conditional agreement which never became effective, or no contractual acceleration bargain. It should then identify the possible route to payment and the evidence still required, while keeping formation, performance and valuation separate.

The following matrix provides a suitable working structure for recording the evidence and each competing contractual analysis:

6. Applied tutorial: disputed acceleration payment

6.1 Project record

Marshfield Developments Ltd engaged Alderstone Construction Ltd to design and construct a private hospital for GBP 14.8 million. The amended contract required completion by 30 November and provided liquidated damages of GBP 60,000 for each week of culpable delay. Variations were to be instructed in writing by Marshfield's project director, while any change to the completion date or contract sum required a document signed by a director of each company.

By late May, delayed design information and slower procurement placed the completion forecast in December. Responsibility for that forecast delay remained disputed between the employer and contractor throughout the acceleration discussions. Marshfield needed the hospital available for clinical commissioning during October and asked Alderstone to investigate acceleration. The contract contained ordinary variation valuation provisions but no express acceleration clause.

At a meeting on 5 June, Marshfield's project director stated that the employer would "pay all reasonable additional costs if Alderstone accelerates and achieves completion in early October". Alderstone's commercial director answered that the company could accelerate by introducing night shifts, parallel commissioning and air freight, although a programme and price would follow. The signed meeting record stated that the parties had "agreed the principle of acceleration, with target and commercial adjustment to be finalised".

On 6 June, Alderstone issued acceleration programme A17 showing completion on 11 October. Its covering email identified additional supervision, night working, air freight and revised commissioning, with forecast additional cost of GBP 780,000. The project director replied: "Proceed with A17 immediately because Marshfield accepts the programme solution. Commercial adjustment will be agreed when the cost review has been completed." Neither company director signed that exchange.

Alderstone commenced night working on 7 June, placed an air-freight order and engaged additional commissioning personnel. Marshfield extended site access, brought its medical-equipment contractor forward and issued design information against the dates in A17. Internal Marshfield emails recorded that implementation of A17 could avoid six weeks of anticipated delay to clinical commissioning.

On 20 June, Marshfield's quantity surveyor offered GBP 350,000 "subject to board approval, completion by 4 October and signature of the formal variation". Alderstone rejected the amount and date, stating that A17 and its GBP 780,000 forecast remained applicable. Thereafter, Alderstone continued the acceleration measures while the project director continued issuing coordination directions against A17.

On 15 July, Marshfield's managing director wrote that the employer "agrees to make an additional acceleration payment, assessed fairly after completion and capped at GBP 600,000, subject to agreement of the final account and execution of the formal variation". Alderstone's commercial director replied that Alderstone accepted the GBP 600,000 cap but could not accept any condition linking acceleration payment to the final account. Neither company subsequently executed the formal variation contemplated within Marshfield's conditional payment proposal.

During August, Marshfield certified GBP 120,000 described as "on-account acceleration cost without agreement of entitlement or final value". The certificate referred to A17 and recorded progress against the 11 October date. Alderstone accepted that expressly qualified payment while reserving its position concerning the unpaid balance of the acceleration claim.

The works achieved practical completion on 10 October, one day before the completion date shown within acceleration programme A17. Alderstone claimed GBP 742,000 of recorded additional labour, plant, logistics and commissioning cost. Marshfield denied further liability, contending that Alderstone supplied no consideration beyond its existing completion duty, that every communication remained subject to agreement or approval, that the amount and target were uncertain, and that the signed-variation requirement was never satisfied.

Alderstone contended that it assumed an earlier completion obligation and supplied additional consideration through the measures in A17. It relied upon Marshfield's avoided commissioning delay, the coordinated performance, the on-account certificate and the completed acceleration. Alderstone argued that the parties concluded an agreement no later than 6 June, alternatively that Marshfield could not rely upon the signature provision after directing and receiving the accelerated performance.

6.2 Assignment

Advise Alderstone's commercial director in a reasoned opinion containing between 1,500 and 2,000 words. The advice must address the following matters arising from the acceleration record:

1. whether the 5 June meeting created an acceleration variation or recorded an agreement in principle;
2. whether programme A17 and Marshfield's 6 June reply identified a sufficiently certain completion obligation;
3. whether Alderstone promised legally defined performance beyond the completion duty imposed by its existing contract;
4. which practical benefits Marshfield obtained and whether Williams v Roffey Bros applies;
5. whether the available communications or surrounding circumstances support any properly reasoned allegation of economic duress;
6. whether the price language created an objective valuation mechanism or reserved future agreement;
7. the legal effect of Marshfield's conditional offer dated 20 June and Alderstone's express rejection of its terms;
8. whether the 15 July exchange produced agreement upon the cap and payment conditions;
9. the effect of the contractual signed-variation provision when applying the reasoning in Rock Advertising;
10. the evidential effect of the parties' coordinated performance, certification process and subsequent on-account payment;
11. the authority of the project director, quantity surveyor and company directors; and
12. the formation date, operative terms and valuation route of any acceleration arrangement found to be enforceable.

Any opinion should apply Williams v Roffey Bros, Wells v Devani, RTS Flexible Systems and Rock Advertising. It should distinguish additional contractual performance from practical benefit and should analyse formality separately from consideration, intention and certainty.

6.3 Acceleration agreement schedule

Complete the following schedule before drafting the opinion and selecting the proposed contractual route:

7. Tutor's commentary

The 5 June meeting supplies evidence of commercial intention but probably does not establish a completed variation by itself. Marshfield promised reasonable additional cost if early-October completion was achieved, while Alderstone promised to develop the programme and price. The signed record expressly states that both the target and commercial adjustment remained to be finalised. Those matters appear central to the proposed exchange rather than details awaiting mechanical calculation.

Programme A17 materially improves the certainty position by identifying 11 October, the acceleration measures and the forecast cost. Marshfield's 6 June reply accepts the programme solution and directs immediate implementation. Its reservation that commercial adjustment will be agreed later creates the central difficulty. Alderstone can argue that reasonable additional cost under the 5 June promise supplies an objective valuation standard, while Marshfield can argue that the parties reserved price for a later bargain.

The available evidence provides Alderstone with a stronger consideration case than Marshfield's defence acknowledges. Alderstone's existing obligation required completion by 30 November, whereas A17 sought completion on 11 October through identified additional measures. A promise to accept an earlier contractual completion obligation would constitute fresh consideration without dependence upon practical benefit. The evidence must establish that Alderstone assumed that legal obligation rather than merely forecasting improved performance.

If the completion obligation remained unchanged, Marshfield nevertheless obtained identifiable practical benefits. The internal emails record anticipated avoidance of six weeks' commissioning delay, while the revised access and equipment arrangements show reliance upon A17. Williams v Roffey Bros may therefore support consideration for an additional-payment promise, provided the variation was not procured through duress and the other formation requirements are satisfied.

The supplied record contains no express threat by Alderstone to breach the original contract unless further money was promised. Alderstone responded to an employer request, proposed defined measures and continued performance while price remained disputed. Marshfield may investigate whether Alderstone withheld resources already required under the contract, but the present facts do not establish illegitimate pressure. The employer's commercial urgency cannot, without evidence of illegitimate pressure from Alderstone, establish economic duress.

Marshfield's 20 June communication is a new conditional offer rather than confirmation of the 6 June position. It proposes GBP 350,000, a 4 October completion date, board approval and formal signature. Alderstone expressly rejects both the proposed amount and the substituted completion target. Continued work after that rejection cannot ordinarily constitute acceptance of the rejected offer, particularly because Alderstone repeats reliance upon A17.

The 15 July exchange also fails to produce an exact documentary match. Marshfield proposes a fair assessment capped at GBP 600,000, but makes payment conditional upon final-account agreement and formal execution. Alderstone accepts the proposed monetary cap while expressly rejecting Marshfield's final-account condition. Its reply is therefore a counter-offer rather than unqualified acceptance of Marshfield's complete proposal.

The August certificate provides evidence that Marshfield treated acceleration as having practical and financial consequences. Its reference to A17 supports identification of the operative programme, and the payment confirms that Marshfield recognised at least an on-account valuation. The express reservation of entitlement and final value prevents the certificate from proving agreement upon the full GBP 742,000 claim or the GBP 600,000 cap.

Separately, the signed-variation provision presents a separate obstacle under the reasoning in Rock Advertising. The contract requires a document signed by one director from each company for changes to completion and contract sum. None of the alleged agreements satisfies that contractual writing and signature requirement. The 15 July exchange involved both companies' commercial decision-makers, but the responses did not contain matching terms and no single compliant variation was executed.

Alderstone's prospective estoppel argument requires evidence extending beyond the disputed informal promise itself. It will rely upon the instruction to proceed, Marshfield's coordinated performance, the cost incurred, the certificate and the employer's receipt of early completion. Marshfield will rely upon repeated reservations concerning later agreement, board approval, final-account settlement and formal signature. The result will depend upon whether Marshfield unequivocally represented that the variation was effective despite the signature clause.

There is a credible alternative that Marshfield instructed acceleration measures under the existing contract's variation machinery without agreeing a revised completion obligation. On that route, Alderstone may obtain valuation under the original contract while the completion date and liquidated-damages position remain unchanged. The instruction power, valuation provisions, notices and certification history must be examined before treating the case solely as a separate acceleration bargain.

A preliminary conclusion is that consideration and the 11 October target can be established more readily than a concluded price agreement and compliance with formality. However, the 6 June exchange may create an objectively workable instruction linked to A17, but its reservation of commercial adjustment and the signed-variation clause weaken the wider contractual-variation case. Complete contract and authority evidence may support payment under the existing valuation machinery even if the separate variation argument fails.

The final opinion requires the unamended and amended contract, delegation records, all versions of A17, cost-review minutes, board papers, valuation calculations, certificates, payment records, notices, programme updates and communications concerning the signature clause. Without those records, a categorical conclusion upon the payment route or revised completion obligation would exceed the available evidence.

8. Tutorial questions

1. What consideration did Alderstone provide beyond the obligations imposed by the original contract?
2. If no earlier completion obligation arose, which practical benefits could satisfy Williams v Roffey Bros?
3. Why does the signed 5 June record indicate agreement in principle rather than completed agreement?
4. Does "reasonable additional cost" provide an objective valuation standard on these particular facts?
5. Which communication first identifies a sufficiently certain acceleration target and defined performance measures?
6. Why does the 20 June proposal cease to be available after Alderstone's express rejection?
7. Which terms in the 15 July exchange prevent corresponding offer and acceptance?
8. What does the August certificate prove, and which contractual matters does it leave unresolved?
9. How does Rock Advertising affect an otherwise certain oral or email variation?
10. Which additional representation and reliance evidence would be required to support estoppel?
11. Could the existing variation machinery provide payment without changing the contractual completion date?
12. Which records are required before advising upon the GBP 742,000 valuation?

9. Assessment standard

An elite answer will analyse consideration, intention, certainty and formality as separate legal requirements. It will identify the original duty before testing fresh performance, apply practical benefit without ignoring duress, and distinguish a future price negotiation from an objective valuation mechanism. Every conclusion should identify the communication, conduct and contractual provision upon which it depends.

Marks should be allocated between the following areas of contractual and evidential analysis:

10. Authorities

1. Williams v Roffey Bros & Nicholls (Contractors) Ltd [1989] EWCA Civ 5; [1991] 1 QB 1, particularly [1991] 1 QB 1, pages 15 to 23.
2. Wells v Devani [2019] UKSC 4, particularly paragraphs 17 to 19 and 58 to 63.
3. RTS Flexible Systems Ltd v Molkerei Alois Müller GmbH & Co KG [2010] UKSC 14, particularly paragraphs 45 to 56 and 81 to 89.
4. Rock Advertising Ltd v MWB Business Exchange Centres Ltd [2018] UKSC 24, particularly paragraphs 10 to 18 and 20 to 32.
5. Chappell & Co Ltd v Nestlé Co Ltd [1959] UKHL 1; [1960] AC 87.
6. Pao On v Lau Yiu Long [1979] UKPC 17; [1980] AC 614.
7. Stilk v Myrick (1809) 2 Camp 317.
8. Pakistan International Airline Corporation v Times Travel (UK) Ltd [2021] UKSC 40, particularly paragraphs 78 to 80.
9. Foakes v Beer (1884) 9 App Cas 605.
10. The Law Debenture Trust Corporation plc v Ukraine [2023] UKSC 11, particularly paragraphs 39 and 40.
11. Scammell v Ouston [1941] AC 251.
12. Courtney & Fairbairn Ltd v Tolaini Bros (Hotels) Ltd [1975] 1 WLR 297.
13. Emirates Trading Agency LLC v Prime Mineral Exports Private Ltd [2014] EWHC 2104 (Comm).
14. Ganz v Petronz FZE [2024] EWHC 635 (Comm), particularly paragraphs 178 to 181.
15. Dunlop Pneumatic Tyre Co Ltd v Selfridge & Co Ltd [1915] UKHL 1; [1915] AC 847, particularly [1915] AC 847, pages 853 to 855.

11. Suggested answers to the tutorial questions

These outline answers indicate the legal reasoning expected from a properly supported response. They are not model paragraphs for reproduction, and each conclusion remains confined to the workshop record stated in section 6.

11.1 Consideration supplied beyond the original contractual obligation

Alderstone's original obligation required completion by 30 November, whereas Programme A17 proposed completion on 11 October through extended working, resequencing, additional supervision and revised procurement measures. If Alderstone promised to assume that earlier completion obligation, the promise imposed performance beyond its existing contractual duty and supplied fresh consideration for Marshfield's payment promise. The distinction between a binding obligation and a programme forecast must still be proved from the communications, because expenditure directed towards an aspirational target would not necessarily establish the promised legal detriment.

11.2 Practical benefits capable of satisfying Williams v Roffey Bros

Marshfield obtained the prospect of avoiding six weeks of commissioning delay, receiving earlier access and coordinating equipment installation against Programme A17. Those benefits were recorded in its internal communications and were objectively connected with Alderstone's continued and accelerated performance. Under Williams v Roffey Bros, an additional-payment promise may be supported where the promisor obtains a practical benefit or avoids a disbenefit, provided the promise was not procured by fraud or economic duress. Consideration would not resolve the separate questions concerning certainty, contractual formality and the valuation mechanism.

11.3 Legal effect of the signed 5 June record

The record expresses a shared commercial objective but states that Alderstone would develop the programme and price, while both the early-completion target and commercial adjustment remained to be finalised. Those matters define the performance sought and the payment promised, so they cannot readily be treated as minor details awaiting clerical completion. The objective question is whether the parties intended immediate legal commitment despite those reservations. Together, the express language and the absence of settled performance measures support an agreement in principle, although the later exchanges may have converted that preliminary position into a more definite arrangement.

11.4 Objective valuation through "reasonable additional cost"

The expression may provide an objective standard where the instructed work, valuation basis and relevant cost evidence permit a court or contractual decision-maker to determine a reasonable amount. Wells v Devani confirms that an intended and acted-upon agreement does not fail merely because objective construction is required to identify a term the parties did not discuss, but the omitted term there was the payment event and the commission rate had been agreed, so the case does not decide that an omitted price may always be supplied. Here, however, the signed record also states that the commercial adjustment remained to be finalised, which may indicate that the parties reserved price for a further bargain. The answer therefore depends upon the whole exchange, the existing valuation provisions and whether "reasonable additional cost" was intended as an operative measure or only as a basis for later negotiation.

11.5 First sufficiently certain target and performance measures

Programme A17, issued on 6 June, first identifies completion on 11 October and describes the acceleration measures, resource changes and forecast cost supporting that target. Marshfield's reply on the same date accepts the programme solution and directs immediate implementation, which materially improves the certainty of the proposed performance. Price remains disputed because Marshfield states that the commercial adjustment will be agreed later. A properly reasoned answer must therefore separate certainty of the required work and target from certainty of payment and formal contractual effect.

11.6 Termination of the 20 June proposal

Marshfield's proposal introduced a payment of GBP 350,000, a substituted completion date of 4 October, board approval and formal signature as connected conditions. Alderstone expressly rejected both the amount and the substituted target, so its response did not accept the proposal and terminated that offer under the ordinary rule governing counter-offers. Later performance cannot accept an offer which no longer remains open, particularly where Alderstone continued to identify Programme A17 as its contractual basis. Any later contract must therefore arise from a renewed offer, a different exchange or conduct referable to another sufficiently certain proposal.

11.7 Terms preventing corresponding offer and acceptance on 15 July

Marshfield proposed a fair assessment capped at GBP 600,000, conditional upon final-account agreement and formal execution. Alderstone accepted the monetary cap but rejected the final-account condition, thereby withholding assent from part of the package Marshfield had proposed. Its response was therefore a counter-offer rather than an unqualified acceptance of Marshfield's conditional proposal. The parties' apparent agreement upon a maximum figure cannot be detached automatically from the conditions attached to it, and the record identifies no later communication accepting Alderstone's revised position.

11.8 Evidential effect and limits of the August certificate

That certificate proves that Marshfield recognised acceleration as having practical and financial consequences, referred to Programme A17 and authorised GBP 120,000 as an on-account payment. It therefore supports Alderstone's case that the employer received and valued accelerated performance. The certificate expressly reserves entitlement and final value, so it does not prove agreement upon the GBP 742,000 claim, the GBP 600,000 cap, a revised completion obligation or compliance with the signed-variation clause. Its evidential value must be confined to what the certifier actually assessed and reserved.

11.9 Effect of Rock Advertising upon an informal variation

Rock Advertising gives contractual effect to a clause requiring specified formalities for amendment, subject to the separate possibility of an estoppel upon sufficiently clear facts. The Marshfield contract requires a document signed by one director from each company for changes to completion and contract sum. None of the identified exchanges constitutes one matching document executed in that manner. Even if the parties reached objective agreement upon performance and valuation, the absence of the required signatures presents an independent barrier to enforcing that agreement as a contractual variation.

11.10 Representation and reliance evidence required for estoppel

Alderstone would need evidence that Marshfield unequivocally represented that the acceleration variation had legal effect despite non-compliance with the signature requirement, together with reliance upon that representation and circumstances making departure from it unjust. The instruction to proceed, coordinated performance, expenditure, certification and receipt of early completion may form part of that evidential case. Repeated references to later commercial agreement, board approval, final-account settlement and formal signature point in the opposite direction. The disputed informal promise cannot alone establish the separate representation required to answer the contractual formality.

11.11 Payment through the existing variation machinery

Yes, if Marshfield validly instructed defined acceleration measures under the original contract and those measures fall within its variation power and valuation machinery. That route could permit valuation of additional resources or changed working methods while leaving the contractual completion date and liquidated-damages regime unchanged. It differs from a bilateral acceleration agreement which substitutes an earlier completion obligation. The complete instruction provisions, valuation rules, notices and certification record must be examined before selecting either route or determining whether both were advanced in the alternative.

11.12 Records required before advising upon the GBP 742,000 valuation

A reliable opinion requires the complete contract and amendments, every revision of Programme A17, the instruction and notice record, daily labour and plant returns, procurement commitments, subcontractor accounts, cost ledgers, valuation calculations, certificates and payment records. It also requires the baseline and updated programmes, progress records, mitigation evidence, cost-review minutes, authority records, board papers and communications concerning the signature clause. Those materials would permit separation of instructed acceleration cost from original obligations, inefficiency, unrelated delay and unproven forecast expenditure. Without them, any conclusion upon the claimed amount would exceed the evidence supplied.

Scope of the lesson

This lesson concerns consideration, contractual intention and certainty under English law as applied to construction variations and acceleration arrangements. It provides an educational method for analysing project records and does not determine any live entitlement. Advice upon an existing dispute requires the complete contract, variation formalities, authority records, governing law, communications, performance evidence and valuation material.