[2025] EWHC 1931 (KB)

ClientEarth describes itself as an environmental law charity which has campaigned for many years for greater action to be taken to reduce air pollution in the UK and the EU. One of ClientEarth’s key workstreams is its “Dieselgate” project. The overarching aim of this project is to reduce nitrogen oxide (‘Nox’) pollution by tackling the continued use of prohibited defeat devices (‘PDDs’) in diesel vehicles.

Mums for Lungs describes itself as a grassroots organisation that campaigns to improve air quality across the UK, with over 1,500 supporters across the UK. It claims a particular interest in the circumstances in which any historic PDDs operated and what impact these devices have had, including if those PDDs exposed members of the public and Mums for Lungs supporters to NOx levels above the applicable legal limits; in understanding fully whether the issues with PDDs are continuing in light of its concern that diesel cars operating PDDs or without adequate emissions regulation systems might still be on the roads in the UK; and in ensuring regulators and those responsible for public health and safety have access to all relevant information to ensure they can protect the public from the effects of excess emissions.

The Scottish NOx Emissions Steering Group represents claimants in various proceedings in Scotland, which are currently being litigated in the Court of Session. The claims being brought are similar to those being considered by this Court in the Pan NOx litigation.

The Court also received correspondence from the Ella Roberta Foundation, Asthma & Lung UK, Deutsche Umwelthilfe e.V., a German environmental protection association, T&E UK (the national office of the European clean transport NGO), the Financial Times and Reuters supporting the applications by the Interested Parties (‘the Supporting Interested Parties’).

For each Defendant group, there is a Generic Particulars of Claim, Defence and Reply. These documents are presently designated non-confidential in their entirety, and as such these documents are unredacted and all three groups presently have access to these pleadings.

There are, in addition, ‘Individual Particulars of Claim’ (‘IPOCs’), directed at a particular sample vehicle within the cohort. By way of example, there are 16 IPOCs for the Mercedes Defendants, and lesser numbers for other Lead Defendants, reflecting the number of sample vehicles originally determined for each GLO. There are a smaller number of Individual Defences (‘IDefs’), reflecting the reduction in the number of samples as the management of the litigation continued, and a Consolidated Reply to Individual IDefs.

These documents have been redacted by the Lead Defendants. The redacted versions have already been made publicly available to those who wish to access them through a bespoke online system facilitated by the parties at the Court’s request.

Whilst each Lead Defendant has been responsible for its own redactions, there is significant commonality of approach. All Defendants have redacted parameter values. The Mercedes Defendants have redacted firmware version string numbers, the names of correction factors, map names, formulae, the names of certain alleged devices, information as to how the Extended Glow Plug Heating Device works, and the entirety of Schedule 4 of each IPOC containing the map names and graphs demonstrating how the alleged PDDs operate. The Ford Defendants (‘Ford’) have redacted formulae, quantitative information, and calculations. Of the Schedules, they redact all map names, maps, and graphs. Prior to providing lesser redacted versions on the evening of 1 July 2025, PCD redacted Ki factors, D and d numbers, and whole passages as to how the alleged defeat devices are said to operate. The revised redactions redact parameters, and maps/graphs derived from the firmware, more closely following the approach of the other Lead Defendants. The Renault and Nissan Defendants redact formulae, as well as all map names, maps and graphs in Schedules 4 and 5.

The Interested Parties plainly have not had the benefit of knowing what lies behind the redactions, unlike the Claimants, although the general nature of the type of information sought to have been redacted is clear from the surrounding context of the unredacted pleadings. The categories of redactions are generally as follows:

A typical redaction of parameters values, taken from a footnote within the Mercedes IPOC for Sample Vehicle MBC1, looks as follows:

The thresholds are identified in narrative form, but the technical string name has been redacted, as have the upper and lower values for the relevant parameter. The redactions made to the narrative explanations of alleged defeat devices combine the various types of redactions. So, by way of example, a particular defeat device is alleged against the Mercedes Defendants by reference to the way in which a correction factor is applied to the EGR (exhaust gas recirculation) rate. The introduction to this section of the pleading, as redacted, reads as follows:

The allegation relating to this particular (unidentified, in the redacted version) correction factor reads as follows:

Typically, Schedule 4 to each pleading contains ‘Graphs and Data’ for the Sample vehicle in question. These have been redacted in their entirety.

By way of further example in respect of another Lead Defendant, the Nissan Defendants (‘Nissan’), the Claimants make allegations within the IPOC for Sample Vehicle ND1 relating to a Glow Plug post-heating strategy, the purpose and effect of which was to optimise the effectiveness of the ECS during NEDC testing. These have been redacted as follows:

Again, as with all Lead Defendants, the Graphs and Data in Schedule 4 have been redacted in full. The principal distinction, however, between the other Lead Defendants and Mercedes is that Mercedes maintain that all the redacted data within the pleading should be Red i.e. only referred to in a closed Court during which only parties who are members of the Pan-NOx CRO may be present. The other Lead Defendants contend (on the whole) that the parameters and values can be regarded as Amber. They can therefore be referred to in open court, and following the concession made during the hearing, with no restrictions on reporting. They maintain a need for the pleadings publicly available upon application pursuant to CPR 5.4C(1) to remain redacted.

Mr McCay contends that the starting point is that the Interested Parties do not need to justify why they want or need a copy of the unredacted pleadings. They rely upon the dicta of Vos J, as he was then, in News Group in which he said that the reasons why an applicant under CPR 5.4C(1) wants the unredacted pleadings are of little or no importance unless it can be said that the document is sought for some improper purpose. There is, rightly, no suggestion that any of the Interested Parties are seeking unredacted pleadings for any ‘improper purpose’.

Notwithstanding this primary position, the Interested Parties nevertheless do provide a justification for seeking unredacted versions of the pleadings.

Emily Kearsey provided evidence on behalf of ClientEarth. Ms Kearsey has run ClientEarth’s ‘Dieselgate’ Project since 2024. Ms Kearsey has explained that the main strands of the project have been to engage with vehicle market surveillance authorities in the UK and EU to prompt robust, wide-ranging investigations into the suspected use of PDDs, and recalls where non-compliance is established; to seek to increase transparency in relation to the ongoing legacy of Dieselgate; and to gather and disseminate evidence to increase public awareness of the impact of continued suspected use of PDDs. Pursuant to the first of these strands, ClientEarth has submitted legal complaints to the vehicle market surveillance authorities in the UK and elsewhere. In 2023, ClientEarth alleged that the DfT’s Article 51 investigation duties were engaged in relation to various vehicle models containing what have, in other European market surveillance reports, been identified as thermal window defeat devices. A second complaint in 2023 alleged that DfT’s Article 51 investigation duties were engaged in respect of other potential strategies. ClientEarth also made representations to the Court in respect of documents disclosed in the context of the KBA Issues Trial, in which, as explained above, the Court determined that the redacted information was irrelevant to any Interested Parties’ ability to understand the issues then before the Court, and as such permitted limited redactions to remain. The judgment made clear, however, that the position may be very different in the context of the PDD trial.

Ms Kearsey gives examples of the ways in which the current redactions to the pleadings are said to hamper the public’s ability to understand how the PDDs are alleged to operate, and importantly, whether they would operate for most of the year in the UK. Referring by way of example to the Glow Plug post-heating strategy, extracted from the Nissan IPOC above, Ms Kearsey contends that the redactions applied to these sections make it difficult to understand anything meaningful about how the Glow Plug Device is said to operate or the nature of the contrast between the two sets of temperatures. Various other examples identify that, by virtue of the redactions, it is generally impossible to understand the nature of the applicable parameters to any alleged PDD at all. In relation to the graphs and data within Schedule 4, Ms Kearsey states that if the schedules contain data relating to the parameters within which the alleged PDDs are operative, that information is of real interest to both the public and market surveillance authorities, and should not be redacted.

Jemima Hartshorn, of Mums for Lungs, makes broadly the same point. She states that as a result of the redactions, the pleadings are impenetrable, and that there is a strong public interest in understanding how any PDDs operated at a detailed rather than generic level. Ms Hartshorn makes the point that whilst no findings have yet been made by the Court as to whether any of the Sample Vehicles do in fact contain one or more PDDs, it is already clear from the IPOCs and IDefs that there are circumstances in which the vehicles’ emissions control systems were deactivated or operated less effectively. The redactions mean, she says, that she and other members of the public cannot understand the circumstances in which the vehicles may emit higher levels of NOx because certain thresholds for temperature, speed, torque or other variables have been met, and it is not possible to tell whether there are circumstances which are likely to occur regularly when driving in England and Wales or whether there are steps that the public can take to avoid them.

Mr McGuire is a partner at Thompsons Solicitors and provided a witness statement on behalf of the Scottish NOx Emissions Steering Group. At the heart of his evidence is the concern that it was difficult to imagine how the detailed technical evidence could be explored effectively by the Court without full details being presented, given that investigation of the parameters and values ‘forms the de quo’ of the PDD trial. Mr McGuire concluded that it would be difficult if not impossible to follow the case without this material being made available.

The Supporting Interested Parties made submissions which, between them, emphasised the importance of open justice, the very substantial public interest in the NOx Emissions litigation, and the impact of the nature and extent of redactions on the ability to report accurately and comprehensively on the case.

The Claimants support the Interested Parties’ application in respect of the pleadings. Mr Kramer KC makes the point, first, that investigations into parameters and values lie at the very heart of the allegations made. To the extent that parameters and values are to be treated as Red, this would mean large parts of the case (in relation to Mercedes) would have to be conducted behind closed doors. At a practical level, there would be an enormous, and unjustified, burden in the preparation of evidence and submissions in redacted and unredacted forms. Even if the parameters and values are Amber, the redaction to the publicly available pleadings means that those who do not attend the trial would not know what the allegations were. Mr Kramer KC fairly accepted that the use of an Amber category as latterly proposed, where no redactions would be required for documents shown on screen and the content of all and any parameters would be capable of reference in open court, would no longer make the trial unworkable or impractical. However, he reiterated the principled stance that redactions to the pleadings remained incompatible with open justice and unjustified in circumstances where the Lead Defendants have not discharged the burden of demonstrating why the information ought to be treated as confidential at all. In this regard, Mr Kramer KC’s submissions emphasised (in summary): (1) the information’s scope and age and (2) the fact that at least some of the information is in the public domain/in the hands of competitors already or capable of identification through chip-tuning or on road testing or collaboration; and (3) the principle of iniquity. Mr Kramer KC submits that in very large part, the approach of Cockerill J in Cavallari provides the answer to the application.

Each of the Lead Defendants opposes the lifting of redactions to the pleadings, notwithstanding the concession by some that the parameters and values can be referred to in open court, and reported if so referred to at the forthcoming PDD Trial. The basis for this is the remaining commercial confidentiality in the information, for the reasons set out more fully below.

The starting point is, as contended for correctly by the Interested Parties, that the substance of the allegations against each Lead Defendant is wholly impossible to follow, at least at any level of technical detail, with the pleadings in their redacted form. Ultimately the case is about the technical detail; this will lie at the heart of the evidence explored at trial. Whilst it may be that various of the Interested Parties may wish to understand that technical detail for reasons collateral to the issue of the advancement of open justice, this does not detract from their submission that, equally, without sight of the parameters and values, they have no hope of being able to understand the issues between the parties.

This has, in substance, been conceded by those Lead Defendants who have accepted that the values and parameters should be designated as ‘Amber’, with no restrictions on their reference in open court and their reporting. It is on this basis that they contended, under their initial proposal, that anyone in Court would be able to ‘follow along’ (but not report or use collaterally), implicitly accepting that if the public were prevented from seeing the detail of the evidence on parameters and values, they would not be able to ‘follow along’.

Even if the parameters and values had been established as being highly commercially confidential, the fact that this information is so central to being able to understand the issues within the trial, together with the significant and justified public interest in this litigation, combine to justify the Interested Parties’ application pursuant to CPR 5.4C(1) for unredacted versions of the pleadings. The importance of the public being able to understand the substance of the claims against the Lead Defendants outweighs any commercial confidentiality in that material. It should not be necessary for a member of the public or journalist to physically attend Court to understand the allegations. The distinction is arbitrary and contrary to the principle of open justice embedded in CPR 5.4C(1).

This conclusion is also demanded in circumstances where, for the reasons set out below, the Lead Defendants have failed to establish at any level of specificity that there is any meaningful confidentiality remaining in the parameters, values and engineering strategies given the passage of time, regulatory change and obsolescence.

Each of the Lead Defendants has given evidence about the iterative design of engines and the retained confidentiality of technical design detail which may, if released, give competitors an advantage. So, for example:

However, all of this evidence has remained at a largely generic level. There is no specific evidence that the very parameters found in either Euro 5 or early Euro 6 vehicles, which are the subject of the pleaded allegations, are still directly relevant to Euro 6d or Euro 7 designs. This is perhaps unsurprising where the regulatory landscape has fundamentally changed (not least as a result of the very matters which are in dispute in this litigation). As pointed out by Mr Kramer KC, on the basis of evidence provided by Mr Gallagher for the Claimants, the early Euro 6b and c vehicles that are the subject of this litigation have not been capable of sale since 1 September 2019, and the parameterisation for the NEDC test has not been possible since 2017 (i.e. 8 years ago). The introduction of RDE (Real Driving Emissions) testing has meant that fundamental changes were required to the way vehicles functioned to capture a far wider range of driving. For example, to meet Euro 6d standards, Ford, Renault and Nissan all introduced SCR (Selective Catalytic Reduction), and there has been no explanation as to why the (superseded) parameters in a non-SCR vehicle would be of any assistance to a competitor developing SCR cars.

Importantly, therefore, there is no detailed explanation, beyond assertion, as to how or why the publication of parameters which form part of an overall iterative design process, but which themselves are older than 5 years, could actually be used by competitors to parameterise their vehicles in any meaningful sense today, against a different regulatory background and where those vehicles have been subjected to their own, separate, iterative design process. Although I accept that those engineers who have given evidence have a genuine, almost instinctive, belief in the confidentiality attached to now long superseded technical developments, in the absence of concrete examples of how such parameters would realistically be of practical use, I regard the suggestion that these parameters would be of any serious use to a competitor developing a vehicle today, which is required to comply with modern Euro standards, as not credible.

It is perhaps because of this that some of the evidence served seeks to rely upon the fact that other parts of the world are still permitted to manufacture cars to old Euro standards, such that the parameters and values may be of remaining value. So, Mr Gaulmé explains that Morocco still operates standards “equivalent to Euro 5” and that, as a result, “Renault’s competitors which operate in the Moroccan market could be interested in obtaining the ECS Code to help shortcut the development of Euro 6 vehicles for sale in Morocco” and, further, that these competitors may also be interested in their Euro 5 code that “may betray technical information that could be used by competitors”. However, this evidence is again wholly non-specific. For example, there is no evidence that any competitor is in fact seeking to develop cars solely for such a market. There is no explanation of what restrictions do or do not exist within the Moroccan (or other) legislation that would make the use of such parameters of conceivable assistance in the development of a vehicle, or how parameters iteratively developed for a Renault vehicle would successfully translate to an unidentified competitor developing a different vehicle to unidentified standards.

Similar, but even more generic, references by PCD to vehicles manufactured in China do not assist them in rebutting the presumption that public knowledge of the old parameters and values in the Sample Vehicles designed to meet (or not, as the case may be) superseded standards are now, through the passage of time, likely to present no meaningful risk of damage to them.

A further point of difficulty for the Lead Defendants, as pointed out by Cockerill J in Cavallari, is their argument of heterogeneity. Each Defendant relies to a greater or lesser extent on the assertion that the parameters and values vary, so as to reflect the individual characteristics of the vehicle. This is said to support the argument that a finding in respect of one vehicle may not safely be translated to an equivalent finding in respect of another vehicle. It is difficult to reconcile this submission with the submission that knowledge of the (old) parameters in respect of a particular aspect of one vehicle would be readily or easily applicable to a different vehicle, itself the subject of its own iterative design.

I also accept evidence served by the Claimants that firmware and ECUs are already publicly available for purchase via specialist websites or eBay. Mr Gallagher provides evidence demonstrating that the same or equivalent parameters and values are readily available for sale online in relation to a large number of the sets of firmware. These have been used in the past by experts to produce reports about the existence of PDDs in various vehicle types. Mr Sage submitted, on behalf of Renault, that the links purportedly relating to its vehicles did not in fact link to relevant firmware for the Sample Vehicles, but related instead to other Renault cars. This misses the point. These websites demonstrate the ability of third parties to access and make public the information over which confidentiality is claimed. There is no suggestion that, to those with the technical know-how, this is a particularly difficult or labour-intensive thing to do. It is also of significance, as submitted by Mr Kramer KC, that notwithstanding the public availability of the type of information sought to be redacted (even if not in respect of the Sample Vehicles), the Lead Defendants have not provided any evidence that this public availability has in fact led to any actual damage to their business, for example by an awareness that the information has been used by competitors to short circuit their own design development. The absence of any such real-life impact, where it is clear that much equivalent information is already in the public domain, fortifies the Claimants’ contention that the risk of damage caused by the public availability of parameters and values (indeed, the entire firmware) is more perceived than real.

Finally, I consider that even if the Lead Defendants had persuaded me that the values and parameters remained highly commercially sensitive, in the context of this litigation, the public interest would remain squarely in favour of allowing the pleadings to be available in unredacted form. This is because the allegations disclose prima facie credible allegations of serious misconduct. As Cockerill J found in Cavallari, this is a ground in its own right to defeat a claim to confidentiality over documents in accordance with the principle of iniquity. The argument is more acute still in the context of whether the detail of the pleaded allegations themselves, let alone any disclosure (as was being considered in Cavallari), should obtain the benefit of a cloak of confidentiality which would have the effect of disabling the public from understanding the issues in dispute.

There is therefore no proper justification for retaining redactions in respect of the parameters and values contained within the pleadings.

As to the other elements of the pleadings which have been the subject of redactions:

Therefore, the Interested Parties’ application succeeds in full (as does the related part of the Claimants’ application) and the pleadings are to be made publicly available in a fully unredacted form forthwith.