About 1.6 million diesel car owners allege in the High Court that 14 manufacturer groups fitted defeat devices prohibited by EU Regulation 715/2007. In July 2026, the court found one prohibited device each for Mercedes and Peugeot-Citroën and dismissed all allegations against Ford, Renault, and Nissan. On October 8, 2026, it refused the claimants permission to appeal. A quantum trial on remedies is listed for October 2026.
Latest development Oct 8, 2026
On October 8, 2026, the High Court refused the claimants permission to appeal the July 2026 prohibited defeat device liability judgment on all proposed grounds. The claimants’ lawyers said they would apply directly to the Court of Appeal for permission to appeal. The quantum trial on remedies remains listed for October 2026.
Why it matters
The judgment sets the English law test for a prohibited defeat device, which departs from later authority of the Court of Justice of the European Union (CJEU). The test affects every remaining UK diesel emissions claim and the economics of large opt-in group litigation.
Background
Roughly 1.6 million owners of Euro 5 and Euro 6b diesel vehicles have brought claims against 14 manufacturer groups in the High Court of England and Wales, King’s Bench Division. The claims proceed under a series of group litigation orders known collectively as the Pan-NOx (or Emissions) Group Litigation. The claimants allege that the manufacturers fitted prohibited defeat devices in breach of EU Regulation 715/2007. They say the devices let vehicles pass regulatory emissions tests while emitting far more nitrogen oxides on the road. The claimants seek damages in contract, under consumer statute, and in tort.
The court selected five lead defendants to run a legal-issues and prohibited defeat device (PDD) trial: Mercedes-Benz, Ford, Peugeot-Citroën (part of Stellantis), Renault, and Nissan. The trial addressed what counts as a defeat device under the Regulation and whether particular devices in test vehicles breached it. It ran from October 2025 to March 2026 before Cockerill LJ, sitting as a High Court judge. Dozens of barristers appeared for the many defendant groups. Their chambers included Brick Court, Fountain Court, One Essex Court, Henderson Chambers, Crown Office Chambers, 2 Temple Gardens, Maitland Chambers, and Monckton Chambers.
On July 10, 2026, Cockerill LJ handed down a 369-page judgment that adopted a narrow definition of a defeat device. Under that definition, a device qualifies only if it detects a regulatory test cycle and functions differently, and more favorably to emissions, only when it detects a test. Applying that test, she found one of ten alleged Mercedes devices and one of six alleged Peugeot-Citroën devices to be prohibited defeat devices. She dismissed all allegations against Ford, Renault, and Nissan. The same day, the claimants and Mercedes both said they were considering seeking permission to appeal aspects of the judgment.
In August 2026, the court refused an application by claimants representing roughly 450,000 Mercedes owners to stay the wider litigation and vacate the quantum trial. Those claimants had argued that the lead defendants’ near-total success on liability undermined the case for proceeding immediately to damages. On October 8, 2026, Cockerill LJ refused the claimants permission to appeal the liability judgment on all proposed grounds. Their lawyers said they would apply directly to the Court of Appeal. The quantum trial, listed for October 2026, is to determine damages and other remedies for the affected Mercedes and Peugeot-Citroën vehicles.
Timeline 7 events
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OrderHigh Court refuses claimants permission to appeal PDD judgment
Lady Justice Cockerill refused the claimants permission to appeal any of their proposed grounds against her July 2026 PDD liability judgment. Claimants’ lawyers said they would seek permission directly from the Court of Appeal.
Permission to Appeal Refused by High Court in "Dieselgate"Vehicle Emissions ClaimsUK Court Refuses Permission to Appeal in Diesel Emissions Lawsuits Against CarmakersUK Court Refuses Permission to Appeal in Diesel Emissions Suits Against Carmakers
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HearingHigh Court lists quantum trial on remedies
The trial is to determine the consequences of the actionable breaches found in the July 2026 judgment, including damages and other remedies for affected Mercedes and Peugeot-Citroën vehicles.
High Court finds largely for manufacturers in 'behemoth' diesel emissions litigation
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OrderCourt refuses claimants’ application to stay proceedings and vacate quantum trial
Around 450,000 Mercedes claimants sought to stay the wider litigation and vacate the October 2026 quantum trial pending a possible appeal of the liability judgment. The court refused the application, so the quantum trial remains listed.
Court refuses claimants' application to stay the NOx emissions litigation against Mercedes
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AppealClaimants and Mercedes-Benz signal possible appeals
Leigh Day, acting for around 1.6 million claimants, and Mercedes-Benz both said they were considering seeking permission to appeal aspects of the liability judgment.
Lawyers considering appeal following Dieselgate judgmentMercedes-Benz and Leigh Day Consider Appeals After High Court Dieselgate Ruling
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JudgmentCockerill LJ hands down PDD liability judgment
The court found one of ten alleged Mercedes devices and one of six alleged Peugeot-Citroën devices to be prohibited defeat devices. It dismissed all allegations against Ford, Renault, and Nissan in a 369-page judgment setting the English law test.
Judgment handed down in Diesel Emissions litigation: Court rejects large majority of allegations against car manufacturersJudgment handed down in the Pan-NOx Emissions litigationCarmakers Broadly Win Round One in Massive UK Suits Over Diesel Emissions
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HearingPDD trial concludes after extended hearing
The trial on the correct legal test for a prohibited defeat device, and its application to the lead defendants’ vehicles, had run since October 2025.
Judgment handed down in Diesel Emissions litigation: Court rejects large majority of allegations against car manufacturersDiesel defeat device trial enters final phase as DfT probes 110 models
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HearingProhibited defeat device (PDD) trial begins
The legal-issues and PDD trial against five lead manufacturers (Mercedes-Benz, Ford, Peugeot-Citroën, Renault, and Nissan) opened before Cockerill LJ in the High Court.
Public do not trust car manufacturers as new Dieselgate case begins in High Court
Experimental AI forecast
How it is madeWill the Court of Appeal grant the claimants permission to appeal the July 10, 2026, defeat-device liability judgment by June 30, 2027?
- Claimants get permission to appeal52%
- Claimants’ appeal bid refused or dropped25%
- Still pending on June 30, 202719%
- Owners settle with manufacturers4%
- Resolves by
- Jun 30, 2027in 8 months
- Record confidence
- Medium
The Court of Appeal is more likely than not (52%) to grant the claimants permission to appeal by June 30, 2027. The judgment sets a narrow English test for defeat devices that departs from later CJEU authority and affects every remaining UK diesel claim, which supports a “compelling reason” for appellate review.
How it resolves. Resolves “Claimants get permission to appeal” if, by June 30, 2027, public records show the Court of Appeal granted the claimants permission to appeal the July 10, 2026, PDD judgment on at least one ground. Resolves “Claimants” appeal bid refused or dropped’ if the Court of Appeal refuses permission on all grounds or the claimants withdraw or do not pursue the application. Resolves “Owners settle with manufacturers” if a settlement with the lead defendants ends the appeal effort before a permission decision. Otherwise resolves “Still pending on June 30, 2027.”
Reasoning
Starting point. Applications to the Court of Appeal of England and Wales for permission to appeal civil High Court judgments, especially those raising points of wide public importance: The Court of Appeal grants roughly 30% to 40% of civil permission applications overall. Grant rates run higher for novel points of law with wide effect.
The base rate for civil permission applications to the Court of Appeal is roughly 30% to 40%, but appeals raising important legal questions succeed more often. This case turns on the definition of a prohibited defeat device, affects about 1.6 million claimants and 14 manufacturer groups, and diverges from later CJEU authority, which favors appellate review. The record shows that the trial judge refused permission on all grounds on October 8, 2026, and that refusal moved the refused outcome up nine points and the permission outcome down six from the previous forecast. Trial judges often refuse permission in cases the Court of Appeal later takes, so the refusal is only a modest signal. The claimants have said they will apply directly, and well-funded claimant firms have strong incentives to press on after losing almost all liability allegations. Paper permission decisions usually take several months, and an oral renewal could push a decision past June 2027, so “still pending” remains material. Settlement is unlikely, since the lead defendants won almost everything and have little reason to pay now. The leading alternative is outright refusal, on the view that the judgment applies settled statutory construction to detailed technical findings of fact.
Narrow defeat-device test diverges from later CJEU authority · Wide effect across 1.6 million claims and 14 defendants · Trial judge refused permission on all proposed grounds · Court of Appeal permission timing and possible oral renewal · Defendants’ near-total liability win reduces settlement pressure
Generated automatically by Claude Opus 5.5 on Oct 27, 2026 from this case’s record on this site, and published without editorial review. The probabilities are the model’s judgment, not measured frequencies, and they are scored publicly as cases resolve. Not legal or investment advice. How the forecasts are made