Ten years after a Volkswagen engineer walked into the US Environmental Protection Agency's offices and admitted the company had been cheating emissions tests on a global scale, the British legal system is attempting to answer a question the original Dieselgate scandal left hanging: was it just VW?
Closing submissions in the Pan-NOx group litigation, officially the largest consumer group action in English and Welsh legal history, began in the High Court today before Lady Justice Cockerill. The three-month evidential phase, which ran from 13 October 2025 to 19 December 2025, has ended. Lawyers representing 1.6 million British drivers now have three weeks to make their final arguments before the judge reserves her judgment. A ruling is expected in summer 2026. If liability is established, a damages trial to determine compensation amounts is already listed for October 2026.
The sum at stake, if claimants succeed across the full pool of 1.6 million vehicle owners, is estimated at up to £6 billion. The question before the court is whether five major car manufacturers fitted diesel vehicles sold after 2009 with prohibited defeat devices: software engineered to detect when a car was being emissions tested and suppress its output, then revert to normal higher-emission operation on public roads.
All five manufacturers deny wrongdoing.
What a Defeat Device Actually Does
The mechanics of the alleged fraud are not complicated, which is part of why the original VW scandal proved so damaging. A defeat device sits within the engine management software. It reads inputs from the car: steering angle, wheel speed, throttle position, ambient temperature, whether the front wheels are being driven or the car is stationary on rollers. Under the specific conditions of an official emissions test, the software activates a suppressed emissions mode. NOx output falls to legal levels. The car passes. It is then driven out of the test facility onto public roads where the suppressed mode switches off and real-world emissions resume.
In some vehicles cited in the current litigation, claimants allege real-world NOx emissions ran at up to 40 times the legal limit, despite test results showing compliance. The cars were marketed as clean diesel. Some buyers paid a premium specifically because they believed they were purchasing a lower-emission vehicle.
The Centre for Research on Energy and Clean Air estimated that defeat devices in UK and EU diesel vehicles have contributed to more than 205,000 premature deaths since 2009, including approximately 22,000 in the UK, along with 41,000 new cases of childhood asthma. These figures represent the excess mortality attributed to the gap between tested and real-world emissions, not total emissions from diesel vehicles overall.
The Five Manufacturers on Trial
Lady Justice Cockerill is hearing evidence against five lead defendants, chosen to streamline proceedings and produce a judgment that will bind claims against a further nine manufacturers who face identical allegations:
Mercedes-Benz gave evidence from 29 October to 6 November. Its spokesperson told the BBC ahead of the trial that the mechanisms involved in its emissions testing were justifiable from a technical and legal standpoint.
Ford gave evidence from 10 to 18 November. The company denies all claims.
Peugeot-Citroën (Stellantis) gave evidence from 18 to 27 November.
Renault gave evidence from 1 to 9 December.
Nissan gave evidence from 10 to 19 December.
The vehicles under direct examination are 20 sample diesel models produced between 2012 and 2017. If the judge finds those vehicles contained prohibited defeat devices and that this gives rise to private law claims for breach of contract and breach of statutory duty, the outcome will determine the legal position for all 1.6 million claimants and will bind the further nine manufacturers currently awaiting their turn in separate but related proceedings.
Those nine additional manufacturers facing equivalent claims include Vauxhall/Opel, Volkswagen Group, BMW, Jaguar Land Rover, Hyundai-Kia, Toyota, Volvo, Mazda and FCA/Suzuki. The International Council on Clean Transportation, the same US-based research group that uncovered the original VW scandal in 2015, has estimated that up to 6.9 million vehicles currently on UK roads may be using illegal emissions technology based on real-world emissions monitoring data.
How This Differs From the Original Dieselgate
The 2015 VW scandal was a confession. VW admitted to US regulators, under the specific threat of criminal prosecution and a potential ban from the American market, that it had used defeat device software across its diesel range globally. That admission gave claimants in subsequent civil litigation a foundation they did not have to prove. VW settled the UK group action in 2022, paying £193 million to 91,000 British drivers, an average of around £2,100 per claimant.
The current litigation has no equivalent admission. Every manufacturer named as a defendant denies wrongdoing. The claimants must prove their case on the technical evidence: expert testimony on how the specific software operated, what it did under test conditions versus real-world driving, and whether the legal definition of a prohibited defeat device covers the mechanisms used.
That legal definition became more complicated following Brexit. EU type approval law, which established the original prohibition on defeat devices that the 2020 High Court ruling against VW was based on, no longer applies directly in the UK. The claimants' legal team argued in opening submissions that the judge is free to look at EU and other foreign judgments as persuasive authority, telling the court there is a compelling body of international legal analysis supporting the claimants' position. Lead counsel Tom de la Mare KC told the court that the law supports the claimants' case at every turn.
The defendants' position, outlined in submissions over the evidential phase, centres on the argument that the software mechanisms in their vehicles served legitimate technical purposes such as protecting engine components and managing thermal conditions, and that these purposes are specifically exempted from the defeat device prohibition under applicable law. The legal battle turns substantially on where that exemption begins and ends.
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The Litigation Behind the Litigation
The Pan-NOx case has had an unusual procedural history that is worth understanding, because it signals the scale and complexity of what is being managed.
The litigation involves 22 law firms and a combined claimant cohort of 1.6 million individuals. Pogust Goodhead and Leigh Day serve as joint lead solicitors. A 2024 High Court ruling described the original claimant legal cost budgets totalling £650 million as absurd and eye-watering, reducing them by approximately 75 percent to £22 million. In a highly unusual development immediately before the trial began, Pogust Goodhead made a voluntary application to stand down as lead solicitor following the departure of co-founder Tom Goodhead and at least five lawyers involved in the case. Lady Justice Cockerill refused the application, ruling that the status quo was the best course.
Martyn Day, senior partner at Leigh Day, said at the start of proceedings: "A decade after the Dieselgate scandal first came to light, 1.6 million UK motorists now get their chance to establish at trial whether their vehicles contained technology designed to cheat emissions tests. It would also mean that people across the UK have been breathing in far more harmful emissions from these vehicles than they were told about, potentially putting the health of millions at risk."
What Happens If the Claimants Win
A successful liability finding this summer would trigger the October 2026 damages trial. Compensation in the VW settlement averaged around £2,100 per claimant. The current case involves a significantly larger claimant pool and allegations that have been characterised as more systematic. If compensation in the Pan-NOx litigation ran at similar levels, the total payout across 1.6 million claimants would approach £3.4 billion. The £6 billion upper estimate reflects higher per-claimant figures in some legal projections based on the wider range of claimed losses including reduced vehicle value, health impact, and misrepresentation of what buyers thought they were purchasing.
Drivers who owned, leased or financed a diesel vehicle made between 2009 and 2020 by any of the manufacturers named in the claim are potentially eligible. The full list extends significantly beyond the five lead defendants. Owners of affected vehicles do not need to actively apply at this stage: the outcome of the liability phase will determine whether claims proceed and on what basis.
The manufacturers could still settle before judgment, as VW did. The scale of the potential damages exposure gives every defendant a financial incentive to assess that option carefully as closing submissions conclude. Whether any of them move in that direction before Lady Justice Cockerill rules will be one of the stories of the next few months.
The original Dieselgate was a scandal that became a confession. This one has been a trial for ten years before it became a courtroom. Whatever the judge decides this summer, the outcome will either confirm that what VW did was an industry-wide practice or establish that the other manufacturers stayed on the right side of the line. Either conclusion will carry consequences that run well beyond the 1.6 million drivers waiting for the answer.
Sources: Law Gazette, 3 March 2026, Pogust Goodhead press release, 13 October 2025, Parkers, Auto Express, Fleet World, Global Legal Post, Consumer Voice UK, GB News, Centre for Research on Energy and Clean Air (CREA) mortality estimates. All manufacturers' positions sourced from court submissions and official statements. All analysis and editorial commentary is original.