Success for Renault and Crown Office Chambers barristers in Diesel Emissions litigation
13th Jul 2026
The High Court (Cockerill LJ) has handed down its judgment on key liability issues in the long-running Diesel NOx Emissions Litigation.
Alexander Antelme KC, David Myhill, Richard Sage and Frederick Simpson represent Renault.
Renault successfully defeated all allegations against them.
Diesel NOx Emissions Litigation
About 1.8 million Claimants pursued claims against car manufacturers and dealers. They alleged that diesel vehicles sold in England and Wales from 2009 to 2017 contain ‘prohibited defeat devices’ or ‘PDDs’. The claims involved allegations of breach of contract, breach of statutory duty and deceit. The Claimants had asserted that the claims were worth billions of pounds.
The claims comprised 13 group litigation orders (“GLOs”), four of which were selected as Lead GLOs. A trial of key liability issues (“the PDD trial”) was heard over 13 weeks from October 2025 to March 2026 to consider whether 20 sample vehicles contained PDDs.
A PDD?
A PDD is a software function which causes a vehicle to operate in a manner prohibited by the relevant regulations, as defined in Articles 3(10) and 5(2) of Regulation 715/2007 (the “Emissions Regulation”):
‘defeat device’ means any element of design which senses temperature, vehicle speed, engine speed (RPM), transmission gear, manifold vacuum or any other parameter for the purpose of activating, modulating, delaying or deactivating the operation of any part of the emission control system, that reduces the effectiveness of the emission control system under conditions which may reasonably be expected to be encountered in normal vehicle operation and use;
The use of defeat devices that reduce the effectiveness of emission control systems shall be prohibited. The prohibition shall not apply where:
a) the need for the device is justified in terms of protecting the engine against damage or accident and for safe operation of the vehicle;
b) the device does not function beyond the requirements of engine starting; or
c) the conditions are substantially included in the test procedures for verifying evaporative emissions and average tailpipe emissions.
The Claimants argued for an extremely broad interpretation of the regulations, and so asserted that “no manufacturer has to date created a calibration that is emissions-compliant across all normal driving conditions”. The manufacturers rejected the Claimants’ approach and argued that the functions about which the Claimants complained were appropriate technical responses to the challenges of combustion across the wide range of driving conditions.
The PDDs alleged in this litigation are distinct from the ‘cheat devices’ alleged against VW and considered by Waksman J in Crossley v Volkswagen AG [2020] EWHC 783 (QB).
Claimants’ approach rejected
Cockerill LJ rejected the Claimants’ analysis of what a PDD was. She found that it “is a device which senses one or more parameters of the test (including its boundary) and objectively operates with the purpose of causing the ECS to work more effectively when it senses that it is being subjected to a test cycle compared to how it works in out of test driving.” In other words, a PDD requires an objective intention to cheat or subvert the regulatory test. As the Judge noted, this “is a conclusion which is a considerable way from the Claimants’ case”.
The Court found no such intention and so no PDDs in the Renault vehicles. The Court reached the same conclusion in relation to Ford’s and Nissan’s vehicles. Limited findings of PDDs were made against Mercedes and PCD.
The Court also determined whether there was an actionable right for damages at civil law, finding that the “statutory scheme properly construed requires the creation of a private law right of action.”
Impact
The judgment is a significant victory for the Defendants. The Judge accepted that the Claimants’ approach was removed from the technical realities of designing and producing a diesel engine. It will doubtless be examined closely in the many jurisdictions where similar claims are proceeding.
The judgment can be found here. A consequentials hearing will take place at a later date.
Two aspects of the judgment are likely to be of wider interest. The first is the discussion at paragraphs 251-263 of the proper approach to post-IPCD CJEU jurisprudence; the Court confirmed that the discretion provided by s6 EU (Withdrawal) Act 2018 is “not confined or defined by a requirement for compelling or weighty reasons” and set out at paragraph 261 the correct approach. The second is the discussion at paragraphs 804-850 of actionability in the context of directly effective EU regulations, and in particular the finding at paragraph 822 that “if the EU parent scheme read as a whole is intended to protect individuals and requires actionability, then that must satisfy the X v Bedfordshire criteria.”
Alexander Antelme KC, David Myhill, Richard Sage and Frederick Simpson are instructed for Renault by Signature Litigation LLP: Tom Snelling, Becca Hogan, Kate Gee, and Tom Crawford.
