Learning purpose

This lesson develops the causal analysis introduced in Lesson 8 by examining the counterfactual question and the difficulties created by multiple causes. The counterfactual asks what would probably have occurred if the event under examination had not happened. That enquiry can expose a missing causal connection, but it cannot decide every case because an event may be necessary without being legally effective, while two independently sufficient events may each defeat a mechanically applied counterfactual.

Successful completion requires the learner to formulate a realistic counterfactual; preserve conditions which would have existed without the examined event; distinguish necessary conditions from effective causes; recognise false positive and false negative results; separate true concurrency from temporal overlap; analyse intervening, sequential and interacting events; apply the contractual allocation of risk; and state conclusions which remain proportionate to the available programme, resource and cost evidence.

1. The counterfactual question as a factual test

The conventional counterfactual asks whether the alleged consequence would probably have occurred but for the event relied upon. In construction claims, that question compares the actual project history with a hypothetical history in which the examined event is removed while other material conditions remain unchanged. If the same completion delay or expenditure would probably have occurred without the event, the event ordinarily fails this preliminary factual test. Where the consequence would probably have been avoided, the event may qualify as a factual cause, although further analysis remains necessary before contractual responsibility follows.

The comparison must be framed around a precise event and a precise consequence. Asking whether the project would have finished earlier without "employer delay" is too general because it conceals the relevant instruction, activity, period and mechanism. A useful question might ask whether commissioning would probably have started on 19 May if the employer had issued the revised control philosophy by its contractual date. Another might ask whether the contractor would have incurred the identified tower-crane standing charge if access to the lifting zone had been provided on the agreed date. Precision permits the proposed answer to be checked against records rather than supplied by assumption.

The hypothetical history must remain realistic and grounded within the recorded circumstances of performance. Removing late information does not justify assuming that labour, preceding work, materials and approved method statements would also have been available unless the records support those conditions. Equally, removing a contractor labour shortage does not permit the analyst to assume that an employer-controlled workface would have been open. A counterfactual which silently repairs every weakness in the claimant's performance proves little because it does not isolate the causal effect of the selected event. The analyst should remove one event, preserve the remaining project conditions and then examine the probable result.

This discipline requires reliable evidence of the position which would otherwise have existed. Accepted programmes may provide planned dates and logic, but they require comparison with progress updates, daily reports, procurement records, labour returns, technical submissions and actual sequence. The programme may show that riser installation preceded pressure testing, yet the technical record may reveal that testing could proceed by isolated section. On that basis, the counterfactual must reflect the physical and contractual dependency which actually governed performance. A displayed logic link is evidence requiring evaluation rather than an automatic statement of cause.

The counterfactual also depends upon the applicable civil standard governing proof of factual propositions. A civil claimant ordinarily establishes factual propositions on the balance of probabilities, so the proposed alternative history need not attain scientific certainty. Nevertheless, probability must arise from evidence rather than from the mere possibility that performance could have improved. Contemporary records showing available labour, completed predecessors and approved materials may support a probable start date. A retrospective assertion that an activity "would have progressed" supplies much weaker assistance where the same period records unresolved access, defective work or missing resources.

The Supreme Court examined the ordinary role of the but for test in Financial Conduct Authority v Arch Insurance (UK) Ltd [2021] UKSC 1. At paragraphs 181 to 185, the Court explained that the test usually operates as a minimum threshold for causation, while also recognising that it can be over-inclusive and produce false negative results. The decision concerned insurance policy wording and losses associated with the COVID-19 pandemic. Its reasoning explains the logical limits of the test, but it does not displace the wording of a construction contract or determine construction entitlement without that separate contractual analysis.

The over-inclusive problem appears where removing an event changes the historical sequence even though the event merely supplied the setting for an independently caused loss. Within that history, the audit failures examined in Galoo Ltd v Bright Grahame Murray [1993] EWCA Civ 3, [1994] 1 WLR 1360 allowed companies to continue trading, so a simple counterfactual could suggest that later trading losses would not have occurred without those failures. At pages 1374 to 1375, however, Glidewell LJ concluded that the alleged failures provided an opportunity to incur losses rather than causing the pleaded trading losses in the required legal sense.

Construction analysis encounters the same error when a preceding event is treated as the cause of everything which follows. Late access might keep a contractor on site when a subsequent mechanical failure stops the affected operation. The access breach remains part of the history, but the claimant must still establish how it caused the particular period and cost claimed. Within this assessment, the counterfactual identifies a possible factual connection; effective-cause analysis, contractual wording and the evidence of each consequence determine whether responsibility follows.

2. Why the but for test cannot decide every causal question

The counterfactual can produce a false positive because many background conditions are necessary to the history without constituting effective causes of the loss. A construction contract, possession of the site and the existence of the completed foundations may each be necessary conditions for a later facade accident, but ordinary legal analysis would not treat them as causes requiring compensation. The enquiry must therefore distinguish conditions which explain why the circumstances existed from events which operated upon the work and produced the particular consequence. That distinction cannot be resolved by grammar, chronology or an unsupported causal label alone.

Galoo illustrates the difference between a necessary historical condition and an effective cause. At pages 1369 to 1375, the Court of Appeal considered whether the alleged audit negligence had caused companies to continue trading and incur losses. The continued trading would not have occurred in the same manner without the audit certificates, yet the pleaded losses arose from what happened during the trading activity. Accordingly, the alleged breach supplied the occasion for the losses without establishing the operative mechanism which produced them. The claimant's causal case required examination of the individual losses and their actual commercial causes.

A comparable distinction appears in construction when an employer instruction changes the project sequence before another event produces the claimed expenditure. Suppose an instruction moves cladding works into winter, after which exceptionally high winds prevent crane operation. The instruction may satisfy a broad counterfactual because the works would not have encountered those particular dates without resequencing. That answer does not alone establish that every weather-related cost was caused by the instruction. The analysis must consider the contractual treatment of weather, the normal incidents of the revised sequence, the foreseeability and reasonableness of the contractor's response, and the direct operational mechanism causing each loss.

A different limitation arises where two independently sufficient causes operate simultaneously and produce a false negative counterfactual. If either of two fires would independently have destroyed the same property at the same time, removing one fire leaves the destruction unchanged because the other remains. A mechanical but for analysis would therefore deny that either fire caused the loss, although together they plainly explain the outcome. At paragraphs 182 to 185 of FCA v Arch, the Supreme Court identified this difficulty and explained why the test cannot be treated as an indispensable rule governing every causal problem.

Construction claims present an equivalent difficulty when two events each prevent the same critical activity during the same period. An employer instruction may close the only available riser while the contractor simultaneously lacks every qualified operative needed for that riser. Removing the instruction leaves the labour impediment, while removing the labour impediment leaves the closed workface. Applied separately and mechanically, each counterfactual would deny causation despite the combined causal reality. The proper enquiry must establish whether each event was genuinely effective, whether each would independently have caused the same delay, and how the governing contract allocates the resulting time and money consequences.

A second multiple-cause category arises when no single event is sufficient, but several events combine to produce the consequence. Reduced labour may slow installation without delaying completion, while restricted access may also be insufficient alone. Their combined effect may exhaust available float and move a critical successor. Removing either event might avoid the completion delay, so both satisfy the counterfactual. That result still does not decide entitlement because the analyst must establish the contribution and contractual treatment of each event, separate recoverable consequences where possible, and avoid allocating loss through unsupported percentages.

At paragraphs 171 to 176 of FCA v Arch, the Supreme Court addressed situations involving concurrent proximate causes and explained that more than one cause may operate effectively. The policy language governed whether the insured peril could produce liability where another cause also operated. That reasoning assists construction practitioners by exposing the weakness of an assumed single-cause model, but the result in any construction dispute remains governed by the relevant contractual provision. An extension-of-time clause, damages claim and loss-and-expense provision may apply different causal language to the same project history.

The test should therefore be used as part of a sequence rather than as a complete answer. First, define the alleged event and the particular consequence requiring causal examination. Secondly, construct the realistic alternative history by preserving every remaining supported project condition. Thirdly, identify every competing or combined cause which remains within that alternative history. Fourthly, decide whether the selected event was an effective cause rather than a background condition or occasion. Fifthly, apply the relevant contractual allocation and the governing legal rule to those findings. Finally, connect each allowed consequence to the evidence and valuation advanced by the claiming party. This method preserves the analytical value of the counterfactual without assigning it work which it cannot perform.

3. Multiple causes, true concurrency and contractual allocation

Multiple causes require careful classification because simultaneous dates do not necessarily establish concurrent causation. Two events may occur during the same week while affecting different activities, resources or completion paths. One event may finish before the second becomes effective, or one may consume float without affecting completion while the other causes critical delay. True concurrency requires more than temporal overlap; each event must operate as an effective cause of the same relevant consequence during the period for which concurrency is asserted.

The relevant consequence must be stated precisely before any asserted concurrency can be assessed properly. Two events may concurrently affect an installation operation without concurrently delaying contractual completion. An instruction and labour shortage might each reduce production in the same zone, while sufficient float prevents either event from moving a completion milestone. Conversely, events affecting different operations may converge upon the same critical successor and jointly delay completion. The analysis should therefore identify the contractual date or cost consequence, trace the controlling sequence, and show how each alleged cause operated upon that same outcome.

In Walter Lilly & Company Ltd v Mackay [2012] EWHC 1773 (TCC), Akenhead J addressed concurrent delay within an extension-of-time assessment. At paragraphs 366 to 370, the judgment treated concurrency as involving two or more effective causes of delay, including an event for which the contractor was contractually entitled to time. The discussion rejected the proposition that a contractor-risk cause necessarily deprived the contractor of the full extension otherwise due under the contractual clause examined. That result depended upon the examined contract and English authority; it should not be converted into a universal rule detached from the agreed wording.

At paragraph 370, Akenhead J distinguished the English approach from the apportionment adopted in the Scottish decision of City Inn Ltd v Shepherd Construction Ltd. Scottish apportionment should never be presented as the governing rule under English construction law. For English projects, the analyst must begin with the applicable contract and English authority, while recognising that factual proof of effective causes remains necessary. A general reference to "concurrency" cannot substitute for demonstrating the activities, dates, critical effect and contractual treatment of each event.

Contract wording may expressly allocate concurrent-delay risk between the parties to a construction project. In North Midland Building Ltd v Cyden Homes Ltd [2018] EWCA Civ 1744, the Court of Appeal considered an amended clause which excluded an extension where contractor-caused delay was concurrent with a Relevant Event. At paragraphs 36 to 38 and 47, the Court gave effect to the parties' express allocation. The decision does not establish a general rule that contractor delay always defeats an extension; it establishes that clear contractual wording can produce that result.

Time and money must also be analysed separately because an extension does not automatically establish recovery of prolongation cost. A contract may provide time relief for a Relevant Event while imposing different conditions for loss and expense. Even where two causes support an extension, the claimant must prove that the recoverable event caused the expenditure claimed. At paragraphs 484 to 486 of Walter Lilly, Akenhead J explained that a claimant advancing an aggregated or global loss case must establish that the relied-on events caused the loss and must account for other causes or make proper deductions where the evidence permits.

The distinction matters where an employer instruction and contractor labour shortage affect the same period. In that analysis, the instruction may support an extension under the contract, while the labour shortage explains some or all of the additional site cost. Alternatively, the contractor may prove that the instruction independently required site establishment to remain for the full period, although labour inefficiency caused separate productivity loss. A reasoned assessment should separate the completion consequence, the prolongation consequence and the disruption consequence before applying the contractual requirements to each.

Multiple causes should not be apportioned through intuition or unsupported impressions of relative responsibility. Percentage allocations require a reasoned evidential basis, such as measured production, resource records, discrete periods, alternative critical paths or an accepted analytical method. Where separation cannot reasonably be achieved, the decision-maker must apply the relevant legal and contractual rules to the proved facts rather than invent precision. A claimant may succeed on one identified head and fail on an undifferentiated balance. An assessor should state what the records establish, what remains uncertain and which further evidence could resolve the uncertainty.

4. Intervening, sequential and interacting events

A later intervening event may alter the causal course leading from the initial event to the claimed consequence. The mere presence of a later event does not automatically extinguish the earlier causal connection. Analysis then concerns the relationship between the events, including whether the later act was a normal response, an ordinary incident of the situation, an independent source of loss or an unreasonable departure from the expected course. The applicable contract and the scope of the obligation remain central because they identify the risks allocated to each party.

At paragraphs 164 to 168 of FCA v Arch, the Supreme Court explained that legal causation is concerned with whether the connection is sufficiently close or direct, applying principles developed by the courts rather than an unguided appeal to intuition. The Court also discussed human intervention within a causal sequence and observed that ordinary actions do not necessarily break the chain. An action may remain part of the ordinary course produced by the original event, while conduct which is wholly unreasonable or erratic may support a different conclusion. The insurance context must again be kept separate from the construction contract under examination.

Construction responses commonly include resequencing, acceleration, alternative procurement, temporary works and resource transfers. A reasonable attempt to mitigate an employer-risk event will not ordinarily become a new cause merely because it introduces another step before the loss. Nevertheless, the claimant must prove why the response was adopted, what alternatives were available and whether the resulting expenditure was reasonable. Records of instructions, planning meetings, option assessments and contemporaneous cost decisions may establish that the response transmitted the original event rather than independently creating the loss.

An unreasonable response can raise different questions concerning causation, mitigation or both. Suppose late access affects one workface, but the contractor removes every operative from all unaffected areas without examining available work. The resulting whole-site loss may not be attributable to the access event merely because the event prompted the decision. Within this assessment, the analysis should identify which resources were genuinely prevented from working, which alternative tasks were available and why the management decision extended beyond the affected operation. The legal classification should follow that factual analysis rather than precede it.

Sequential events require period-by-period analysis of their changing effects upon the relevant consequence. An employer instruction may cause five days of delay before a contractor plant failure causes another four days, producing successive causes rather than concurrency. A later event may also prolong an existing delay, take over as the effective cause, or affect only a different consequence. The analyst should prepare a chronology showing when each event became operative, when it ceased to affect the relevant activity, and whether the completion path or cost consequence changed during the sequence.

Interacting causes arise where one project event materially changes the operative effect of another. Late design information may compress fabrication into a period when specialist capacity is scarce, increasing the effect of an ordinary procurement constraint. Conversely, a contractor's pre-existing delay may mean that information issued after its contractual date still arrives before actual need, producing no immediate project effect. The counterfactual must preserve the other event and test their interaction rather than assuming that the nominal duration of either event equals its effect upon completion or cost.

Evidence of intervening and sequential causes usually requires more than a final programme. Daily records establish actual work and constraints; correspondence explains decisions and available alternatives; labour and plant returns identify resource availability; technical registers establish information dependencies; and cost ledgers connect responses with expenditure. Witness evidence may explain gaps, but it should be tested against contemporary records. A causal conclusion based only upon a retrospective chronology risks confusing events which happened in sequence with events which caused the same consequence.

The final classification should answer three separate questions concerning connection, allocation and provable loss. Its first enquiry asks whether the later event broke, continued or altered the causal connection. Contractual analysis then asks how the agreement allocates each event and its consequences. A final enquiry determines which loss can be proved against each permitted route. Keeping these enquiries separate prevents an assessor from treating every later event as a complete defence or treating every mitigation response as recoverable merely because an earlier breach occurred.

5. Case focus: Walter Lilly & Company Ltd v Mackay

Walter Lilly concerned extensive delay and loss claims arising from the construction of a substantial residential property. The judgment examined numerous alleged causes, programme material and claimed financial consequences. Its lasting value for claims practice lies in the insistence upon examining effective causes within the actual contractual and factual context. The decision does not authorise an abstract concurrency label; it requires the analyst to identify the events which truly caused delay and to apply the extension provisions which the parties agreed.

At paragraphs 366 to 370, Akenhead J addressed the position where two effective causes operate, one qualifying as a contractual Relevant Event and another arising from contractor responsibility. The judgment concluded that the presence of the contractor cause did not, under the clause examined, reduce the extension otherwise due for the Relevant Event. That conclusion followed the particular contractual wording and the English authorities considered within the judgment. It does not remove the claimant's obligation to prove that both alleged events were effective causes of the same delay.

The judgment's detailed evidential discussion provides equally instructive guidance for construction claims specialists. At paragraph 371, the judgment emphasised assessment within the actual factual context, including the available programmes and the sequence shown by the evidence. Paragraph 375 records Akenhead J's criticism of analysis which failed to consider possible causes of delay. At paragraph 380, the judgment discussed prospective and retrospective approaches while recognising evidential limitations created by the absence of a reliable contemporaneous programme. These passages support a record-led enquiry rather than selection of a method which predetermines the answer.

The factual result also demonstrates why concurrency must be proved rather than presumed. At paragraphs 459 to 460, the Court found no contractor-responsibility concurrency which displaced or reduced the contractor's extension entitlement on the matters determined. The result arose from the evidence concerning the causes actually operating upon completion. Practitioners should not cite the case merely to assert that concurrent delay always produces a full extension. They must first prove the effective causes and then show that the contractual provision operates in the same manner.

The judgment's treatment of aggregated loss claims provides a further safeguard against unsupported causal attribution. At paragraphs 466 to 486, Akenhead J examined circumstances in which a claimant may advance a global claim where individual loss cannot sensibly be allocated among numerous events. Paragraph 486 requires proof that the relied-on events caused the claimed loss and requires consideration of other causes. Where an unrelated or claimant-responsibility cause explains part of the loss, the claim must address it through separation, deduction or another evidentially justified treatment.

Accordingly, Walter Lilly supports separate and potentially different conclusions for time and monetary recovery. A contractor may establish that a Relevant Event caused critical delay and obtain the extension supplied by the contract, notwithstanding another effective cause under the wording examined. The same contractor cannot assume that every cost incurred during the extended period was caused by the Relevant Event. Site overheads, labour inefficiency, financing charges and subcontractor accounts each require their own causal proof and contractual route.

The case also cautions against reconstructing a project through a single retrospective narrative. Construction projects contain design development, instructions, resource variation, procurement issues and changing sequence. A reliable assessment identifies those events and tests them against contemporaneous progress rather than treating every adverse condition as part of one employer-caused continuum. Where the evidence supports only a range or provisional result, the conclusion should expose that limit and identify the material needed for a firmer determination.

For claims specialists, the resulting working proposition demands disciplined treatment of every causal stage. Establish the contractual event, identify its effective period, prove the activity and completion consequence, examine competing causes, apply the agreed time provision, and then repeat the causal analysis for every monetary head. A conclusion which compresses these stages into "employer delay caused prolongation" does not satisfy the reasoning demonstrated in Walter Lilly.

6. A construction claims method for multiple causes

The following structured method converts the governing doctrine into a repeatable construction claims assessment:

1. Define one event, including its contractual source, responsible risk and operative dates.
2. Define one consequence, distinguishing activity delay, completion delay, disruption and expenditure.
3. Construct the realistic counterfactual by removing only the selected event from the project history.
4. Record the remaining labour, plant, access, design, procurement and preceding-work conditions.
5. Determine whether the consequence would probably have occurred in that adjusted history.
6. Identify false positives by separating effective causes from conditions, occasions and mere chronology.
7. Identify false negatives by testing independently sufficient and combined multiple causes.
8. Distinguish true concurrency from overlap by proving effective causes of the same consequence.
9. Divide sequential periods where the operative cause or completion path changed.
10. Apply the wording governing extensions, compensation, damages and any concurrency allocation.
11. Connect each allowed consequence to its particular cost evidence and remove unsupported causes.
12. State a conclusion which identifies evidential limits and the records needed for final determination.

Within this assessment, the method should be applied to a cause-and-effect schedule rather than left within narrative submissions. Each row should contain the event, relevant clause, actual dates, counterfactual, affected activity, programme effect, competing cause, contractual allocation, claimed loss, supporting records and provisional conclusion. Separate rows should be used where one event allegedly produces several consequences. This structure allows a reviewer to accept one causal chain without accepting every consequence associated with the same event.

7. Construction workshop: the instruction and the labour shortage

Project record

Harbourside University Developments Ltd engaged Meridian Mechanical Ltd to install mechanical services within a research building. Clause 8.6 permits a fair and reasonable extension where an employer instruction causes completion delay. The clause contains no express exclusion for contractor-caused delay operating concurrently with that instruction. Separate provisions require proof that an employer instruction caused any claimed loss and expense.

The following fictional records form the complete evidential file supplied for this workshop exercise:

Learner assignment

Prepare a reasoned preliminary assessment which addresses each of the following evidential and contractual questions:

1. What precise counterfactual should test the effect of Instruction 41?
2. Which records establish the programme position against which that counterfactual should operate?
3. What evidence supports Instruction 41 as an effective cause of activity delay?
4. What evidence supports the labour shortage as a separate effective cause?
5. Do the events establish true concurrent completion delay or merely temporal overlap?
6. How should independently sufficient causes be tested without producing a false negative?
7. Did the resumption decision or subsequent staffing position break or alter the causal sequence?
8. How does clause 8.6 allocate the established concurrent-delay risk?
9. What extension conclusion can presently be reached under Walter Lilly?
10. What part of the £180,000 monetary claim is presently established?
11. What should an employer-side assessment test before rejecting or allowing the claim?
12. What provisional determination and further-evidence direction should be issued?

Tutor observations

The workshop deliberately separates evidence of event duration from evidence of completion effect. Instruction 41 prevented northern riser work for fifteen working days, but L9-R01 records terminal float and L9-R05 does not isolate the effect of reduced labour. The labour shortage overlapped the instruction, yet L9-R04 records available southern work and does not prove that the missing operatives would independently have delayed the same completion path.

Accordingly, the available record supports firm findings about occurrence and weaker findings about true concurrency, completion delay and money. Learners should resist replacing missing resource and programme analysis with assumptions favourable to either party. A defensible preliminary assessment can recognise Instruction 41 as an effective cause of northern-riser delay while reserving the final completion and cost consequences pending the identified evidence.

8. Common errors in multiple-cause analysis

9. Practitioner checklist

Before presenting or assessing a multiple-cause claim, confirm that the analysis can answer every question below:

1. Has each alleged cause been defined by event, date, contractual source and responsible risk?
2. Has the particular consequence been separated into activity delay, completion delay and cost?
3. Does the counterfactual remove only the selected event while preserving other conditions?
4. Do contemporary records support the resources and dependencies assumed within that counterfactual?
5. Has every necessary condition been distinguished from an effective cause or mere occasion?
6. Have independently sufficient and combined causes been tested for false negative results?
7. Does asserted concurrency concern effective causes of the same consequence rather than shared dates?
8. Have sequential and intervening events been divided into their operative periods?
9. Has the exact contractual allocation been applied separately to time and monetary relief?
10. Does each claimed cost correspond with a proved causal chain and reliable account record?
11. Have contrary explanations been examined and deducted where the evidence supports them?
12. Does the conclusion identify evidential limits without filling gaps through assumption?

10. Authorities and further reading

• Financial Conduct Authority v Arch Insurance (UK) Ltd [2021] UKSC 1, particularly paragraphs 164 to 185 and 197.
• Galoo Ltd v Bright Grahame Murray [1993] EWCA Civ 3, [1994] 1 WLR 1360, particularly pages 1369 to 1375.
• Walter Lilly & Company Ltd v Mackay [2012] EWHC 1773 (TCC), particularly paragraphs 366 to 380, 459 to 460 and 466 to 486.
• North Midland Building Ltd v Cyden Homes Ltd [2018] EWCA Civ 1744, particularly paragraphs 36 to 38 and 47.

11. Suggested answers to the workshop

Answer 1: The correct counterfactual

The assessment should ask whether commissioning and contractual completion would probably have occurred on the L9-R01 dates if Instruction 41 had not suspended northern-riser installation, while preserving the recorded labour availability and every other project condition. This formulation removes only the selected event and avoids assuming eighteen operatives when L9-R03 records fewer. FCA v Arch at paragraphs 181 to 185 explains both the ordinary counterfactual and its limits. A final answer requires an updated programme incorporating actual progress, logic and resource availability.

Answer 2: The evidential baseline

L9-R01 supplies the accepted sequence, planned dates and five working days of terminal float, while L9-R05 records the contemporary controlling activity and later forecast. Those records provide the starting comparison but do not prove the alternative completion date because the later update lacks resource loading and a labour-shortage fragnet. Walter Lilly at paragraphs 371, 375 and 380 requires assessment within the actual factual and programme context. The reviewer needs native programme files, update narratives, logic changes and progress status supporting each forecast movement.

Answer 3: Instruction 41 as an effective cause

L9-R02 proves that Instruction 41 suspended northern-riser installation from 7 to 25 April, while L9-R04 confirms that the affected workface remained inaccessible throughout that period. These records establish an operational mechanism rather than chronology alone: the employer instruction prevented the identified installation activity. Galoo at pages 1369 to 1375 requires an effective cause rather than a mere occasion. Completion effect remains unproved without evidence linking the delayed riser to testing, commissioning, remaining float and the actual post-release sequence.

Answer 4: The labour shortage as a competing cause

L9-R03 proves reduced labour during portions of the suspension period and attributes that shortage to Meridian's transfer decision. It does not prove that the shortage independently delayed completion because L9-R04 records available southern work and six transferred operatives working there. The effective-cause enquiry under Galoo requires proof of what the missing labour changed, while Walter Lilly requires analysis of actual causes. Resource-loaded updates, allocation sheets, planned production and evidence of work available to additional operatives are needed before treating the shortage as effective.

Answer 5: True concurrency or temporal overlap

The present records prove temporal overlap but do not yet prove true concurrent completion delay. L9-R02 and L9-R03 place the instruction and labour shortage within common dates, although L9-R04 shows that the instruction closed the northern workface and that southern work remained available. Walter Lilly at paragraphs 366 to 370 concerns two effective causes of the same delay, not events which merely coexist. A fragnet or reliable retrospective analysis must show whether the labour shortage would independently have moved the same commissioning and completion dates.

Answer 6: Avoiding a false negative

Each event should first be tested for factual effectiveness and then considered within a multiple-sufficient-cause analysis. If Instruction 41 alone prevented northern work and insufficient labour would independently have prevented the same critical progress, removing either event leaves the other and a mechanical counterfactual produces a false negative. FCA v Arch at paragraphs 182 to 185 explains that identified limitation of mechanical counterfactual reasoning. L9-R03 to L9-R05 do not presently prove independent sufficiency, so the assessor needs resource-loaded logic, productivity requirements and evidence concerning deployable qualified labour.

Answer 7: Later staffing and the causal sequence

L9-R07 records resumption with twelve pipefitters and the absence of the requested eighteen-person recovery proposal. That evidence may show a later contractor constraint, but it does not automatically break the effect of the earlier instruction. The enquiry under FCA v Arch paragraphs 164 to 168 concerns whether a later action became an independent cause or remained within the course produced by the initial event. On that basis, the assessment requires planned crew requirements, achievable recovery options, actual production and reasons for Meridian's staffing decision after access returned.

Answer 8: Contractual allocation of concurrency

Clause 8.6 permits a fair and reasonable extension where an employer instruction causes completion delay and contains no express concurrent-delay exclusion. On those stated facts, Walter Lilly paragraphs 366 to 370 provides the relevant English construction analysis if both events become proved effective causes. North Midland paragraphs 36 to 38 and 47 does not supply a contrary default because its result depended upon express allocation wording. The complete executed contract, amendments and incorporated conditions must be checked before any final interpretation is adopted.

Answer 9: Present extension-of-time conclusion

Instruction 41 is proved to have delayed northern-riser installation, but the full fifteen-working-day completion effect is not established. L9-R01 records five working days of terminal float, while L9-R05 forecasts later completion without isolating the instruction from labour or actual progress. Under Walter Lilly paragraphs 366 to 380, entitlement depends upon effective delay and the clause applied to the factual context. A provisional extension may be reserved pending a time-slice or fragnet analysis demonstrating consumption of float and movement of commissioning and completion.

Answer 10: The monetary claim

The £180,000 claim is not presently established because L9-R06 aggregates supervision, welfare, temporary services and labour inefficiency across a period extending beyond the instruction. It does not separate float, unaffected work, labour shortage or post-release staffing. Walter Lilly paragraphs 466 to 486 requires proof that relied-on events caused the loss and proper treatment of other causes. Meridian must provide cost ledgers, resource allocation, baseline expenditure, disrupted-hour analysis and deductions for contractor-responsibility effects before any identified sum can be allowed.

Answer 11: Employer-side assessment

The employer should accept the documented suspension in L9-R02 and L9-R04, then test completion and cost consequences without assuming that overlap defeats entitlement. Walter Lilly requires identification of effective causes, while North Midland confirms that an adverse concurrency allocation depends upon express wording. The assessment should examine programme logic, float, labour requirements, southern work, recovery options and cost segregation. It should request native updates, resource data and account evidence, then explain separately any allowed time, rejected cost and reserved issue.

Answer 12: Provisional determination and evidence direction

The provisional determination should find that Instruction 41 effectively delayed northern-riser installation between 7 and 25 April, while reserving the precise completion extension and rejecting the present £180,000 valuation as unsupported. L9-R01 to L9-R07 do not prove independently sufficient labour delay, actual float consumption or causal cost allocation. Galoo, FCA v Arch and Walter Lilly require effective-cause, multiple-cause and contract-specific analysis. The direction should require programme files, resource loading, productivity records, recovery evidence and cost-ledger allocation before final determination.

12. Knowledge check

An accompanying ten-question Knowledge Check examines realistic counterfactuals, false positive and false negative results, effective causes, true concurrency, intervening events, contractual risk allocation, separate time and money analysis, and the workshop evidence. Each question requires reasoned application of doctrine rather than recollection of an isolated phrase.

Closing point

The but for question remains a useful factual discipline, but it becomes unreliable when treated as a complete legal rule. Construction claims require the analyst to identify effective causes, confront multiple and later events, apply the contract, and connect every allowed consequence to contemporary evidence.

Scope of the lesson

This lesson provides professional training on English contract-law principles and construction claims analysis. It does not determine any project entitlement, replace examination of the executed contract and full evidential record, or provide legal advice concerning particular facts. Authorities and contractual provisions must be checked in their current form before application to a live dispute.