Vorsprung durch quantum: Court refuses claimants’ application to stay the NOx emissions litigation against Mercedes 

10/08/26

On 10 July 2026, Lady Justice Cockerill handed down the liability judgment in the Pan-Nox Emissions Group Litigation (see our news story here) (the “PDD Judgment”). Cockerill LJ found that only 1  of 10 alleged Mercedes devices constituted a prohibited defeat device (PDD). In respect of the other Lead Defendants: 1 out of 6 alleged Peugeot Citroen devices was a PDD and none of the alleged Ford, Renault or Nissan devices were PDDs. 

In light  of these findings, the Claimants, including the c.450,000 Mercedes claimants, applied to vacate the quantum trial listed for October 2026 and to stay the entirety of the proceedings against all the manufacturers pending a possible appeal against the PDD Judgment.

The Claimants’ position was that in light of the Lead Defendants’ overwhelming success on liability, the quantum trial was now deprived of content and should be postponed. They relied in particular on the reductions in sample Claimants giving evidence, Core Sample Vehicles being considered, and PDDs in play.  They submitted that if they succeeded on appeal, the quantum trial would be redundant or that much of the work would be wasted. The Claimants’ application was supported by every Lead Defendant except Mercedes. 

Mercedes submitted  that the autumn listing should continue. The case management to date had always envisaged that there might be a narrowing of the issues after the PDD Judgment. More importantly, even if it proceeded only against Mercedes the quantum trial remained capable of determining critical questions of law and related methodological principles which would be applicable across the Pan-NOx proceedings and which could provide a platform for future case management. As such, there was real utility in proceeding. A stay would risk wasting  very substantial costs already incurred getting the quantum trial to the PTR, as well as years of delay while any appeal was resolved. 

In a reserved judgment dated 7 August 2026, the Court (Mr Justice Constable) dismissed the Claimants’ application and the supporting submissions of other Lead Defendants, and concluded that the better course was that the quantum trial should go ahead against Mercedes. Constable J accepted Mercedes’ analytical framework and (at [47]-[77]) discussed the issues of general application Mercedes submitted would be decided. The judge concluded that it was entirely possible that the Court’s judgment as to whether the Claimants’ approach to quantum was, in whole or in part, legally sustainable would be “dispositive in practice of the issue of how quantum is to be assessed across the Pan-Nox Litigation”. 

Similarly there was (at [86]) “a real prospect that determination of the quantum issues will materially advance, and may assist in unlocking, the litigation from a commercial perspective.”  When weighed in the balance, the modest (in the context of this litigation) costs of proceeding to the quantum trial outweighed the risks that some of that work would be wasted or would need to be repeated.  In those circumstances, the Court considered “it makes clear sense to proceed”. 

The full judgment can be found here.