Background
The Pan-NOx Emissions Group Litigation comprises approximately 1.6 million claims against 16 vehicle manufacturers. In an earlier liability judgment, [2026] EWHC 1753 (KB), the court rejected most of the claimants’ allegations concerning prohibited defeat devices but found that a Mercedes coolant-temperature setpoint device and a PCD split-injection device were prohibited defeat devices in certain sample vehicles. Mercedes and PCD were accordingly found liable in relation to vehicles containing those devices, while the other lead manufacturers were not found liable on the allegations tried.
The claimants intended to seek permission to appeal the liability judgment and applied to vacate the quantum trial scheduled to begin on 26 October 2026 and to stay proceedings meanwhile. Ford, Nissan and PCD supported a stay; Mercedes and Renault did not. The court proceeded on the assumption, without deciding the merits, that there was a realistic prospect of permission to appeal being granted and that an appeal could change the litigation landscape.
The claimants argued that the much smaller pool of surviving sample claims was no longer representative and that a reduced quantum trial would provide little useful guidance, potentially requiring another trial after an appeal. Mercedes maintained that the trial could still decide broadly applicable questions about valuation, the assessment date, mitigation, credit for vehicle use and damages for distress.
The Court’s Holding
Mr Justice Constable refused the stay in the Mercedes group litigation order, allowing the reduced Mercedes quantum trial to proceed. He held that the trial retained real utility despite involving only three Mercedes sample claimants. It could determine important questions of legal principle, materially narrow future disputes, assist settlement and potentially avoid or reduce the scope of a later Pan-NOx quantum trial.
The court concluded that spending an estimated further £8 million on the Mercedes trial was justified by even a modest prospect of avoiding a future full quantum trial estimated to cost approximately £45 million before inflation. Substantial resources had already been invested, and postponement would cause delay, waste preparatory costs and increase the expense of restarting the process.
The court granted the stay for the other lead group actions, including PCD. It declined to compel PCD’s participation because neither side in that group wished to proceed and the marginal benefit of adding PCD was outweighed by the additional cost. Non-Mercedes lead parties could nevertheless make submissions at the Mercedes trial and, if they did, would be bound by the resulting findings of law.
Key Takeaways
- The Mercedes quantum trial remained scheduled despite the claimants’ intended appeal from the earlier liability judgment.
- A reduced trial may proceed where it retains a real prospect of resolving or narrowing broadly applicable legal issues and substantial preparation costs have already been incurred.
- The other lead group actions were stayed, while their parties retained the option to participate through legal submissions and thereby be bound by the findings of law.
Why It Matters
The ruling preserves a near-term vehicle for deciding the central methodology for valuing Pan-NOx claims, including whether damages should reflect hypothetical warranted and actual values, which date should govern assessment, and how later events such as software updates and vehicle use affect recovery.
Those determinations could shape the commercial resolution of claims across the wider litigation even where they are not formally binding. The judgment also illustrates the High Court’s willingness to alter different group actions’ timetables separately when balancing appeal risk, trial utility, party participation and the proportionate use of judicial and litigation resources.