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Lawyers for 1.6 million motorists seek permission to appeal Dieselgate trial judgment

Lawyers representing motorists at the Dieselgate trial will seek permission to appeal the trial judgment at a High Court hearing from 7-8 October 2026

Posted on 28 September 2026

The judgment, handed down on 10 July following the 13-week trial, found that just three of the 20 representative vehicles examined had breached emissions regulations.

The three vehicles - one Mercedes and two Peugeot/Citroen models – were found to have contained so-called Prohibited Defeat Devices (PDDs), which meant they were designed to reduce their emissions output under test conditions compared to when driven on the road. 

The other 17 vehicles, manufactured by Mercedes, Peugeot/Citroen, Ford, Renault and Nissan, were found by the judge to contain devices that did not meet the court’s definition of a PDD and therefore did not breach emissions regulations.

The judgment creates a significant divergence between the legal position in England and Wales compared with much of Europe after the court decided post-Brexit not to follow several key decisions of the Grand Chamber of the Court of Justice of the European Union (CJEU). This means defeat devices likely to be unlawful in the EU are currently permitted in England and Wales.

The claimants’ lawyers will seek to appeal the judgment on the following grounds:

  • The judge's interpretation of Article 3(10) of the Emissions Regulation led her to adopt an overly narrow definition of a PDD, requiring the presence of a specific type of test-recognition device similar to those in Volkswagen vehicles found to have cheated emissions tests at a previous High Court hearing in 2020.
  • The court’s judgment is inconsistent with several CJEU authorities and places England and Wales in a materially different position from the EU on defeat device law.
  • The claimants believe the judge's approach to "normal driving conditions" should be re-examined as it may have been defined too narrowly.  

In her judgment, Lady Justice Cockerill made contingent findings on alternative interpretations of a PDD if she is wrong in her interpretation of the law (Article 3(10) of the Emissions Regulation 2007); if those contingent findings were accepted, then a majority of the sample cars would have an unlawful defeat device.

Leigh Day’s senior partner Martyn Day said:

“Our appeal will argue that the judge applied too narrow a definition of what constitutes a Prohibited Defeat Device and that some of the technical evidence around this issue should be looked at again.

“Despite the manufacturers’ denials, the judge found that Mercedes and Peugeot/Citroen did install unlawful defeat devices in some of their vehicles. It is our clients’ belief that the other vehicles examined also contained prohibited defeat devices in their cars.

“In her ruling, the judge has contradicted established EU law on what a defeat device is. We will be urging her to allow this appeal to the Court of Appeal to go ahead and avoid England and Wales becoming the only places in Europe that allow manufacturers to build and sell cars containing these types of devices.”

Pogust Goodhead’s lead partner for the Pan-Nox case Anna Varga said:

"We have carefully considered the July judgment. Our clients consider several of the findings should be appealed, including the overly narrow interpretation of what constitutes a prohibited defeat device. It creates a divergence with much of Europe with potentially serious implications both for emissions levels and motorists in England and Wales. 

“The Court itself recognised the significance of this issue: if its interpretation is ultimately found to be wrong, the majority of the sample vehicles would contain prohibited defeat devices in breach of the Emissions Regulation based on the Court's own contingent findings. That is not a minor point of law. It goes to the heart of these claims and deserves to be tested.

“There are some 1.6 million motorists in this litigation and our responsibility to them is unchanged. This litigation is about accountability, and we will continue to pursue their claims with determination and rigour. Seeking permission to appeal is the necessary next step.” 

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Martyn Day

Martyn Day

Martyn is the joint founder of the firm and is the senior partner

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Lawyers representing 1.6 million vehicle owners are considering whether to seek permission to appeal following today's High Court judgment in the Dieselgate trial

Following a 13-week trial, after considering 20 representative vehicles across five car manufacturers, a High Court judge found that three vehicles – one Mercedes and two Peugeot/Citroen models – contained Prohibited Defeat Devices (PDDs).

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