Key facts
- Lawyers for 1.6 million motorists will ask the High Court for permission to appeal a ruling on diesel emissions tests.
- The appeal application is scheduled for October 7-8, 2026.
- A July judgment found three of 20 representative vehicles contained Prohibited Defeat Devices (PDDs).
- The court's definition of a PDD was found to be too narrow by claimants.
- Claimants argue the ruling conflicts with EU law on defeat devices.
Lawyers representing approximately 1.6 million motorists are seeking permission from the High Court to appeal a recent judgment concerning alleged 'defeat devices' in diesel vehicles. The appeal application is scheduled to be heard on October 7 and 8, 2026.
In July, Lady Justice Cockerill ruled that three out of 20 representative vehicles examined contained Prohibited Defeat Devices (PDDs), which are designed to alter emissions performance during testing. These vehicles included one Mercedes and two Peugeot/Citroen models. However, the court found that the remaining 17 vehicles, including models from Mercedes, Peugeot/Citroen, Ford, Renault, and Nissan, did not contain devices meeting the court's legal definition of a PDD.
The claimants' legal team contends that the court adopted an overly narrow interpretation of the regulations, particularly Article 3(10) of the Emissions Regulation 2007. They argue this interpretation places too much emphasis on technology similar to that found in Volkswagen vehicles and conflicts with decisions from the Court of Justice of the European Union (CJEU). This divergence, they claim, could allow some defeat devices unlawful under EU rules to be permitted in England and Wales.
Additionally, the claimants are challenging the interpretation of 'normal driving conditions,' arguing it was interpreted too narrowly. They suggest that alternative interpretations considered by the judge indicate a majority of the 20 vehicles could be found to contain unlawful defeat devices if the appeal court adopts a different regulatory interpretation. Martyn Day, senior partner at Leigh Day, stated that the appeal will argue for a broader definition of a PDD and that some technical evidence requires re-examination. Anna Varga of Pogust Goodhead noted that clients consider several findings should be appealed, including the narrow interpretation of what constitutes a defeat device.