The High Court has largely rejected a landmark 'dieselgate' claim brought on behalf of 1.6 million UK car owners, ruling that most emissions-control strategies used by manufacturers did not amount to illegal defeat devices. Lady Justice Cockerill stated that 'not every calibration or emissions-control strategy amounts to a defeat device' and that proving an intention to rig tests was necessary.
Key Ruling and Implications
The judgment, delivered after a 15-week trial between October 2025 and March 2026, focused on 20 vehicles from Mercedes, Ford, Renault, Nissan, and Peugeot/Citroën. The judge found that in most cases, the challenged strategies did not constitute prohibited defeat devices, but noted that some technologies used in Mercedes and Peugeot-Citroën cars could be considered non-compliant. The ruling binds not only these manufacturers but also others not directly involved in the trial.
Reactions from Manufacturers and Claimants
Manufacturers welcomed the verdict. Mercedes-Benz said the court ruled 'very largely in favour' of the company, though it is considering an appeal over the vehicle deemed non-compliant. Stellantis, owner of Peugeot-Citroën, also plans to appeal the upheld allegations. Nissan stated it had always maintained its technologies were not defeat devices, while Renault affirmed its cars complied with all regulatory requirements. Ford was contacted for comment.
Claimants' lawyers expressed disappointment. Martyn Day, senior partner at Leigh Day, said: 'The high court has found that despite their denials, other manufacturers also used VW-style defeat devices. The judge has also found that many other defeat devices are lawful because she surprisingly disagreed with the established EU case law on what a defeat device is.' Anna Varga of Pogust Goodhead noted the judgment 'does not bring this litigation to an end' and adopted a narrower interpretation of the law than elsewhere in Europe.
Background and Broader Context
The case, the largest group action trial in English legal history, stems from the 2015 Volkswagen dieselgate scandal, where VW engines were designed to operate differently under test conditions. The claimants argued manufacturers engineered vehicles to reduce NOx emissions in tests compared to real-world driving. The judge acknowledged that testing is difficult to interpret and that alternative approaches could have found more defeat devices.
Next Steps and Campaigner Response
Claimants are considering an appeal, citing a significant divergence between UK and EU law. Campaign group Mums for Lungs called the ruling a 'setback', but director Jemima Hartshorn said: 'Whatever the courts have found, it does not change the scientific consensus – that these diesel cars are toxic. It’s important that the two car companies found guilty today act swiftly to remove their vehicles and compensate for their actions.'
