High Court ruling leaves car owners uncertain

In a landmark judgment, the High Court has ruled on the controversial Dieselgate trial, prompting lawyers representing 1.6 million vehicle owners to contemplate an appeal. Following a comprehensive 13-week trial, the court identified that three of the examined models – one from Mercedes and two from Peugeot/Citroen – were found to contain Prohibited Defeat Devices (PDDs). In contrast, the judge determined that the defeat devices installed in vehicles from Ford, Renault, and Nissan did not contravene Emissions Regulations, highlighting a significant divergence between legal interpretations in Great Britain and the rest of Europe.

Lady Justice Cockerill, delivering the opinion, asserted that Peugeot/Citroen and Mercedes had employed unlawful VW-style cycle recognition defeat devices in some vehicles; nevertheless, she expressed reservations about whether the Mercedes device significantly impacted nitrogen oxides (NOx) emissions in the evaluated vehicle. Notably, the judge opted not to align with several critical rulings from the Grand Chamber of the Court of Justice of the European Union (CJEU), establishing a unique legal landscape in Great Britain where defeat devices deemed illegal across the EU could still be permissible.

The judge articulated her willingness to reconsider her interpretation, indicating that should it be incorrect, a majority of the sample cars would indeed house unlawful defeat devices. With respect to Ford, she concluded that the devices in question did not qualify as defeat devices while refraining from addressing outstanding issues regarding serious defects in Ford’s Lean NOx Trap (LNT) emissions control technology.

Martyn Day, senior partner at Leigh Day, representing the various claimants stated, "The High Court has found that despite their denials, other manufacturers also used VW-style defeat devices." He added that the ruling had left significant gaps in accountability and consumer protection, prompting the firm to explore the possibility of an appeal.

Anna Varga from Pogust Goodhead echoed similar sentiments, asserting, "Today's judgment does not bring this litigation to an end." She underscored their ongoing commitment to advocating for the rights of the 1.6 million motorists involved. Richard Barnes, a Mercedes owner and claimant, expressed disappointment, cautioning that the judicial interpretation of what constitutes a defeat device might provoke a disparity in regulations between Great Britain and the wider European context.

This monumental case, which commenced in October 2025, marked the most extensive group claim trial in English and Welsh legal history, scrutinising the actions of 14 car manufacturers. The trial initially focused on five lead defendants: Mercedes, Ford, Renault, Nissan, and Peugeot/Citroen, with further claims anticipated against additional manufacturers, highlighting the extensive implications of the Dieselgate scandal on the automotive industry and consumer trust.