Following the handing down of the Prohibited Defeat device (PDD) judgment on 10 July 2026, in which Lady Justice Cockerill found that only 3 of the 20 sample vehicles (1x Mercedes and 2x Peugeot/Citroen) contained prohibited defeat devices, all focus turned to what happens next. This included whether the quantum trial, listed to start in the autumn would still go ahead? And if so, in what form?
At a hearing on 24 July 2026, Mr Justice Constable who is the Managing Judge presiding over the quantum side of the litigation, grappled with these questions. After hearing submissions by both sides, he determined that the quantum trial will still go ahead, but only in respect to the Mercedes vehicle model that was found to contain a PDD. In his judgment he concludes that the reduced scope of the Quantum Trial does not deprive it of real utility and that the determination of the quantum issues will not only advance the litigation in that ALL Defendants will be bound by its legal findings, but it will also narrow, if not resolve future disputes and increase the prospect of settlements.
Aside from the quantum trial, the parties will return to Court in early October to hear arguments about matters arising from or ‘consequential’ to the PDD judgment. Among the issues on the agenda will be costs consequences flowing from the judgment. This hearing will also serve as the opportunity for each side to formally request permission to appeal the PDD judgment. The Claimant’s appeal is likely to focus on the judge’s surprising decision not to follow existing European case law and instead adopt a very narrow definition of what a defeat device is. This decision attracted as much surprise and criticism from academics as it did from lawyers. Any grounds of appeal that Lady Justice Cockerill does not grant at the hearing are likely to be heard by another judge at a further hearing following written submissions of the parties. Given the unusual nature of the judgment, in that contingent findings (resulting in many more vehicles containing PDDs) were provided by Lady Justice Cockerill in an alternative ruling of what a PDD is and her expectation that an appeal would follow, we expect that the appeal hearing will go ahead.
Once the appeal timetable is set and the quantum trial commences, further updates will follow.
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