Which cognitive biases were evident in Carillion plc's collapse?

5 bias patterns are documented in this case, led by Optimism Bias. The full set: Planning Fallacy, Sunk Cost Fallacy, Groupthink, Framing Effect, Overconfidence Bias. Each is mapped to Decision Intel's 22-bias R²F taxonomy with stable IDs and academic citations.

Did these cognitive biases cause Carillion plc's collapse?

Decision Intel identifies reasoning-risk indicators correlated with poor outcomes — it does not claim to establish causation. That honesty is the procurement weapon: a CSO can defend a score that names the risk indicators a committee should pressure-test, not one that pretends to prove the cause. Optimism Bias and the other documented patterns were detectable in the reasoning before the outcome was known; whether they caused it is a question no audit can settle — too many other factors (market, timing, execution) are in play. A reasoning audit names the risk indicators a committee should pressure-test, not a verdict it should accept.

What is Decision Intel's reasoning audit?

Decision Intel runs a Recognition-Rigor Framework (R²F) audit on strategic memos, detecting cognitive biases from a 22-bias canonical taxonomy and producing a Decision Quality Index (DQI) score. The audit produces a hashed, tamper-evident Decision Provenance Record (DPR) suitable for audit-committee review.

All case studies

Catastrophic failureFinancial Services2018

Carillion plc

Carillion Collapse

Estimated impact: £7B in liabilities; 43,000 jobs at risk

F14

Decision Quality Index (simulated)

Critical · 5 biases detected, 3 toxic combinations

UK construction and outsourcing giant Carillion collapsed with £7B in liabilities and a pension deficit of £2.6B. The board continued paying dividends and awarding bonuses while the company was insolvent, using aggressive accounting to delay recognition of contract losses.

Decision context

Whether to continue bidding aggressively on low-margin government contracts and paying dividends despite deteriorating cash flow and mounting contract provisions.

Deep hindsight-stripped analysis coming soon. This case is part of our ongoing backfill to reconstruct what was flaggable in the record at decision time. The summary and bias profile below are drawn from primary sources.

Decision anatomy

Monetary stakes

Very high

Dissent suppressed

Yes

Time pressure

Present

Unanimous consensus

Yes

Decision participants

Dissent encouraged

External advisors

Iterative process

Red = risk factor present · Green = protective factor present

Biases present in the decision

Planning Fallacy

medium

Sunk Cost Fallacy

high

Groupthink

high

Framing Effect

medium

Overconfidence Bias

high

★ Primary driver · Severity estimated from bias type and decision outcome

3D Decision Knowledge Graph

Carillion plc · 5 biases, 3 toxic combinations

Drag to rotate · Scroll to zoom · Click to explore

Decision

Critical

High

Medium

Toxic

Bias Intensity Profile

Severity × confidence across 5 detected biases

Toxic combinations

!Optimism Trap

Overconfidence and availability bias create a systematically positive outlook that ignores base rates.

!Sunk Ship

Commitment to a failing course escalates to justify sunk costs, even as evidence mounts.

!Conglomerate Fallacy

Far-adjacency acquisition justified by target growth and brand halo with no answer to "why us as parent" — Porter parenting-advantage absent.

The curated library this case sits in

Across all 155 curated case studies in our library, by documented outcome:

123

documented failures

partial / mixed

documented successes

The library is curated toward documented failures, so this split describes the library, not the base rate of deals. The case above is one row in it.

■ Failure■ Partial■ Success

Lessons learned

Optimism bias in contract accounting delayed loss recognition until positions were irrecoverable
Paying dividends from a cash-negative company is a framing effect that signals health while destroying value
Government procurement that selects the lowest bidder without assessing contractor financial resilience creates systemic risk

Source: UK Parliament Joint Inquiry into Carillion, HC 769 (2018) (Case Study)

Pilot slots available

These patterns were flaggable in Carillion plc's own record — before the outcome.

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Workflows that fire on decisions like Carillion plc’s

The same Recognition-Rigor Framework that documents this case audits memos in the same shape — before the outcome forces the lesson.

For CSOs and Heads of Strategic Planning

Strategic memo audit

Audit a strategic memo for cognitive bias and forecast errors before the board sees it.

Audit a strategic memo

For Heads of Corp Dev and M&A advisors

M&A bias audit

Audit an acquisition thesis for the three named M&A failure patterns: Synergy Mirage, Conglomerate Fallacy, Winner's Curse.

Audit an acquisition thesis

For Heads of Corp Dev and Investment Committee chairs

IC memo pre-vote stress test

Stress-test an investment committee memo before the vote — catch Synergy Mirage, Winner's Curse, and Conglomerate Fallacy.

Audit your IC memo

See the full audit-tool surface.

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Toxic combinations

!Optimism Trap

Overconfidence and availability bias create a systematically positive outlook that ignores base rates.

!Sunk Ship

Commitment to a failing course escalates to justify sunk costs, even as evidence mounts.

!Conglomerate Fallacy

Far-adjacency acquisition justified by target growth and brand halo with no answer to "why us as parent" — Porter parenting-advantage absent.

The curated library this case sits in

Across all 155 curated case studies in our library, by documented outcome:

123

documented failures

partial / mixed

documented successes

The library is curated toward documented failures, so this split describes the library, not the base rate of deals. The case above is one row in it.

■ Failure■ Partial■ Success

Lessons learned

Optimism bias in contract accounting delayed loss recognition until positions were irrecoverable

Paying dividends from a cash-negative company is a framing effect that signals health while destroying value

Government procurement that selects the lowest bidder without assessing contractor financial resilience creates systemic risk