How the Defendants Won: Remediation, Framing, Resources

What the largest group action in English legal history teaches about remediation, framing and resource depth

Written by Will Whawell. Human intelligence throughout; AI assisted with the drafting.

July 2026

On 10 July 2026 the High Court handed down judgment following the liability issues trial in the Pan-NOx Emissions Group Litigation — the largest group action in English legal history, brought by around 1.6 million claimants against the lead defendant manufacturers, Mercedes-Benz among them. Cockerill LJ, sitting as a High Court judge after a trial that ran from October 2025 to March 2026, rejected the vast majority of the allegations that the sample diesel vehicles contained prohibited defeat devices. Only limited adverse findings survived: a coolant temperature setpoint functionality in certain Mercedes-Benz sample vehicles — removed by a software update rolled out in December 2015 — and a split-injection strategy in certain Peugeot-Citroën Euro 5 vehicles. A damages and remedies trial is listed for October 2026 to deal with what remains (Fountain Court).

That is the factual result. What follows is my reading of it — commentary, not anything the judgment itself says about either side's strategy. But I think the reading is well supported, and it matters for anyone who funds, prices or manages group litigation. This was not a case decided by claimant numbers. It was decided by case theory, evidence and the capacity to sustain both over years. On each, the defendants held the better ground.

The legal test did the heavy lifting

The court adopted a deliberately narrow construction of a prohibited defeat device under the Euro 5 and Euro 6b Emissions Regulation: a device that detects a regulatory emissions test and objectively operates with the purpose of causing the emissions control system to work more effectively during the test cycle than on the road. Proving that a calibration strategy reduced emissions-control effectiveness in real-world conditions was not enough; the claimants needed to establish that test-detecting purpose. Many of the challenged strategies were found to serve legitimate engineering functions — component protection, thermal management — and so fell outside the definition altogether. Notably, the court declined to follow certain post-IPCD authorities of the Court of Justice of the European Union, considering that it had better access to the detailed factual and expert evidence and that aspects of the CJEU reasoning contained errors (Fountain Court).

The defendants did not try to defend every strategy as beyond scrutiny. They concentrated the fight on the statutory definition, presented the calibrations as engineering rather than evasion, and let the construction argument carry the volume of allegations away. The court's test aligned closely with that framing.

Mercedes-Benz: remediation, framing, resources

Three elements of the Mercedes position repay attention.

First, early and documented remediation. The single adverse finding against Mercedes concerned a functionality that had been removed by a software update more than a decade before judgment. Addressing the issue years before trial converted a potential systemic vulnerability into a discrete, time-bound point — identify, fix, document, then defend the fixed position.

Second, the tightly framed technical and legal narrative described above, run consistently across a multi-year procedural timeline.

Third, resource depth. In its official 2025 annual results, Mercedes-Benz Group AG reported group revenue of €132.2 billion (down from €145.6 billion in 2024), reported EBIT of €5.8 billion and free cash flow of the industrial business of €5.4 billion — call it roughly €2.5 billion of revenue a week, my arithmetic rather than the company's. A defendant at that scale can fund extensive expert evidence, sample-vehicle testing, firmware and calibration disclosure, and coordinated case management without the cash-flow pressure that forces early settlement. That capacity does not decide legal questions. It decides how long you can afford to keep asking them properly.

The claimant model met its limits

The claimant side assembled an unprecedented cohort under Group Litigation Orders, with sophisticated case management — lead defendants, sample vehicles, staged trials — underpinned by third-party funding and after-the-event insurance. The machinery worked; the case theory did not. A broad suite of allegations across many calibration strategies failed against the purpose-based test the court applied, testing evidence proved difficult to interpret, and costs budgets had already been heavily scrutinised and cut in earlier case-management phases.

Funder economics sharpen the problem. Funders need returns, which favours volume, high headline valuations and litigating to a binary liability outcome. When the legal definition at the heart of the claim is contested and the court ultimately narrows it, that model leaves little room to adapt: sunk costs are high, adverse-costs exposure is real, and partial discontinuance is commercially unattractive. The adjustments Pan-NOx suggests are the ones good litigation project management has always suggested — tighter selection of the strongest samples and strategies at the outset, earlier work on causation and quantum while liability is contested, realistic recovery modelling after adverse findings, and funding structures that permit staged investment and genuine settlement authority.

What to watch

The October 2026 hearing will define what residual exposure flows from the limited findings that survived. Claimant lawyers are considering appeal routes, not least because of the divergence the judgment opens with aspects of European case law. Separately, Mercedes has substantially drawn a line under its remaining US diesel exposure through a December 2025 multistate settlement with state Attorneys General — a civil penalty of $149,673,750, with $120 million payable upfront and the balance suspended against a consumer relief programme including $2,000 payments to qualifying owners — distinct from the roughly $2.2 billion US federal and civil settlements of 2020.

The lesson for observers of mass claims is uncomfortable but clear: strategy and resources still matter more than scale. A defendant that invests early in remediation and a coherent technical narrative, and can see the fight through, can prevail against even the largest claimant cohort. Claimants and their funders will need to move beyond volume-and-valuation models towards more selective, adaptive, evidence-led tactics — and towards the disciplined case planning that makes those tactics affordable.

Prepared with AI and human input. Part of the Pan-NOx series from T3PS Legal Dynamics.