Project Nutcracker: Would a ‘challenge window’ reduce NSIP judicial reviews?

On the 20 May 2026, Government published a policy paper (“Getting Britain Building: Reforming Judicial Review for Infrastructure”) which floats two new proposals for reducing legal challenges to nationally significant infrastructure projects (“NSIPs”): [here] (the “Policy Paper”). In this Nutcracker I discuss one of them: the provision of a ‘challenge window’ during which complaints about a draft development consent order ("DCO") decision could be drawn to the attention of the Secretary of State and cured.

Separately, look out for my Nutcracker (coming soon) on the Government’s other idea: the rubber stamping of DCOs by Parliament.

How would the challenge window work?

Filling in some of the gaps, it seems that the challenge window would work as follows:

Step 1: The normal DCO application, examination and determination process would be followed (save for a tweak to the final step). This comprises: (i) a developer applying to the Planning Inspectorate (PINS) with all the usual documents; (ii) a circa four-month wait while Inspectors are appointed, the application is advertised and written objections are made; (iii) a six-month examination based on written representations and hearings; (iv) PINS has three months to write up a report and recommendation for the Secretary of State; and (v) the Secretary of State has a further three months to write up his/her decision based on the report. The key difference is that under the proposed new process, instead of actually making a decision and granting the DCO in step (v), the Secretary of State would simply publish a draft decision and draft DCO. Presumably PINS’ recommendation report would be published alongside these draft documents.

Step 2: A ‘challenge window’ would then be open for a period (say six weeks). During this period, objectors would be able to submit representations to the Secretary of State setting out (in effect) the grounds on which they would have brought a judicial review if the actual decision were made in the form contemplated. This could be used to flag alleged errors of law, procedural unfairness, environmental assessment defects, inadequacy of reasons, inconsistencies, or drafting defects.

Step 3: Presumably, although the Policy Paper doesn’t state this, the Secretary of State may need to invite the applicant to respond to the complaints or to submit additional information in order to address them. Presumably also, to ensure procedural fairness, the Secretary of State may need to invite the complainants to respond. And presumably where the new information provided is an update to the environmental impact assessment (EIA), it will need to be advertised more generally and all representations taken into account. The length of this ‘response window’ could not be usefully fixed in legislation as it will depend on what is required case-by-case. 

Step 4: The Secretary of State then takes into account the complaints and information submitted during the ‘challenge window’ and ‘response window’ and makes the final decision. The decision letter could include additional reasoning as compared with the draft, and the DCO drafting could also be changed from the draft version.

Step 5: The usual six-week period for bringing a claim for judicial review before the courts then opens (as it does currently after any DCO is granted). The Policy Paper suggests that: “the courts would have a clearer basis to refuse permission or relief’ based on the foregoing new challenge window process. The Policy Paper hopes that this would make it easier for the court to rule any claim as “totally without merit”, and therefore to not be heard substantively. It also states that: “The law would also be changed such that the courts would refuse permission for a judicial review to proceed on any issue not brought up during the consent process or challenge window.”

The above mechanism is described in the Policy Paper as an ‘optional mechanism.’ This must mean that it would be up to developers to opt into this process as a protection against judicial reviews if they felt it would be useful.

How helpful would a challenge window be? 

Primary legislation would be needed to bring about this new regime. So is it worth it? Would developers want to opt into this type of regime? I set out some thoughts below:

1. A challenge window could address simple corrections and additions

   The proposed regime would work best where the complaint made in the challenge window relates to something that can be rectified by simple rewording of the Secretary of State’s draft decision or the draft DCO. For example, the grounds of challenge brought against the Stonestreet Green Solar DCO in the High Court [details in this previous Nutcracker]. The grounds in that case all essentially related to whether the Secretary of State gave adequate reasons in the decision letter as to why the DCO had been granted, with regard to harm to heritage assets, consistency with a nearby (much smaller) solar scheme and the consideration of alternatives to the project. The case was disposed of by the courts within four months. The judge ruled the three grounds ‘totally without merit’ and commented that the claim was a classic example of the claimant not reading a decision letter or recommendation report ‘as a whole’, but instead seeking to apply an exegetical, overly legalistic analysis. 

   Under the proposed challenge window regime, the three grounds in the Stonestreet Green case could have been flagged to the Secretary of State during the challenge window. The Secretary of State could then have issued his final decision with additional drafting to prevent any perceived grounds for judicial review. 

   If the Secretary of State had made these additions quickly after they were flagged in a challenge window, there would have been some time-saving for the developer, compared with the four months it took to dispose of the judicial review. There would also have been a cost saving for both the Secretary of State and the developer. This of course assumes that the objectors didn’t find new grounds of challenge in the final decision letter (see section 4 and Conclusion).

2. Many grounds won’t be amenable to simple surgical corrections

   The Stonestreet Green judicial review was brought on unusually simple (and weak) grounds. Most of the judicial reviews that we defend have more grounds (ten or so sometimes) – and many of them are not grounds that could be addressed by simple wording changes to the decision letter or the DCO. 

   For example, grounds of judicial review often relate to the way in which a certain part of the environmental impact assessment (EIA) or habitat regulations assessment (HRA) have been carried out. It’s important to note that we usually disagree that there has been any deficiency. In other words, the claimants haven’t caught us out in something we wish we could have corrected if only we’d known. In relation to Gatwick’s DCO, for example, we never believed the claimant’s contention that a different methodology was appropriate for calculating carbon emissions from international inbound flights (and neither did the High Court judge who recently ruled in our favour on the case – more details in section 5 below). Similarly, one of the grounds in the Sizewell C DCO judicial review was that our HRA hadn’t assessed where the project’s long-term water supply would be coming from many years hence (a ground also dismissed by the courts). 

   If a challenge window regime had been in operation, the Secretary of State could have offered Gatwick and Sizewell C the opportunity to collate and present information on these grounds (and the many others) during a response window. But would we have wanted to? How long would that have taken? And would it have stopped legal challenges being brought on other grounds? I think the answers are: no; who knows but quite a while; and no. I expand upon why in the sections below. 

3. The process is likely to spin out of control

   Legally, any updated ‘environmental information’ we provided in the response window would need to be open to all for comment (not just the complainants). One could therefore easily see this process taking a long time (extra seasonal surveys etc), and spinning out of the Secretary of State’s control. It could become more like part of the examination, or the extended decision-making periods we see for DCOs where the Secretary of State has to ask questions or request more information. 

   The Secretary of State might well receive a whole new set of comments and criticisms in the response window. Some might clash. Different sets of objectors might disagree about what a legally sound EIA methodology looks like for a particular topic: particularly for things like route alignments for grid lines or roads, where residents in different areas have different interests. In other words, even if the objective is to address all issues raised by the would-be claimants, this may not be possible. This links to the next point.

4. There will inevitably be new grounds for challenge arising from the actual decision

   It is not going to be possible to avoid the potential for judicial reviews to be brought when the final Secretary of State decision is made. This is because the decision letter will have changed from the draft version published previously. That is the whole point. The decision letter will try to address the issues raised (and new information produced) in the challenge and response windows. But no one will have seen the final decision letter until it is published. There is no suggestion that the updated version will be published in draft …or we disappear down a rabbit hole of never-ending challenge windows. 

   This means, however, that the courts will have to entertain grounds of challenge relating to new points arising from the final decision letter and DCO. To attempt to pass legislation that ousts their jurisdiction to do so would conflict with some foundational principles of constitutional law. Any legislation that purported to do so would test the principle of parliamentary sovereignty as never before. 

   It is quite likely that the changes made between the draft and final versions of the decision letter (and the process used between the two) will give a determined objector grounds of challenge. They might be very weak grounds, and most will fail ultimately, but they still have to be processed by the courts before this conclusion is reached. 

   Knowing this, is a developer likely to opt to use this new challenge window process? The risk (I would say likelihood) is that it lengthens their programme overall: they go through the challenge window/response window process, and still end up having to fight a challenge in the courts afterwards. In some cases the new process might unearth a decent ground of challenge, which might otherwise have led to the DCO being quashed. But I think most developers would take their chance with the current process. After all, even in the (statistically unlikely) event that their DCO were quashed, it is likely to get regranted after a legal cure is applied. 

5. Do we want to pander to unfounded criticisms?

   The other oddity is that the challenge window process only works if the developer/Secretary of State accepts the criticism, and acts on it accordingly (or at least acts on it, even if not agreeing with the criticism). Do we really want to pander to what will usually be unfounded criticisms, which might be onerous to address? Already most of us think that custom and practice in terms of EIA and HRA in the UK is excessive and overly precautionary. New and unhelpful precedents will be set if developers are encouraged to gold-plate their assessments even further in response to all criticisms made in the challenge window. 

   It would have been quite mad for us, for example, to try to pull together an assessment for what long-term water supply solution the regional water company might come up with to supply Sizewell C in more than a decade’s time. The water company themselves hadn’t yet identified its options. That work was part and parcel of a much wider regional water planning strategy which had yet to take place. Any attempt that Sizewell C made at that exercise would have been fatuous, and no doubt a challenge would have been brought by objectors pointing out its flaws.

   The claim against Gatwick’s DCO initially comprised no less than 12 grounds of challenge, on matters including: the Secretary of State's assessment of greenhouse gas emissions, interpretation of aviation planning policy and consideration of noise and economic benefits. We recently won in the High Court on all grounds, with Mr Justice Mould describing the claimant's grounds variously as "without foundation", "[losing] sight of the essential factual and legal context of the decision" and "fanciful" whilst concluding that the Secretary of State’s reasoning was "reasonable, logically coherent, internally consistent and sufficiently explained" and "unarguably lawful and rational". The claimant is hoping to get the Court of Appeal’s permission to hear their case. Whether they obtain that permission or not, I don’t believe it would have been in either Gatwick’s interest or in the interests of UK infrastructure planning in general for Gatwick and the Secretary of State to have tried to address these 12 unjustified criticisms in a challenge window.

6. Preventing people raising things in court that they could have raised (or did raise) during the examination 

   This idea sounds sensible but is oversold. If a legally mandated document like an EIA or HRA is deficient (ie simply does not meet the criteria based on Regulations and case law) then it is ultra vires for the Secretary of State to make a decision based on it – regardless of whether anyone previously pointed this out, or how much the legally correct scope of those assessments was debated at examination. If this were not the case, the Secretary of State could grant a DCO based on one-page documents calling themselves EIA and HRA assessments, and no one would be allowed to question this via the courts if they hadn’t pointed this out at examination (or if they’d pointed it out but the Inspector took an alternative view). This isn’t the case. Decision-makers have wide scope to exercise judgement on matters of fact and the weighting of pros and cons, but whether they have correctly applied and interpreted the law must always be a matter justiciable by the courts. Unfortunately, this limits the benefit of any new legislation which purports to oust the court’s jurisdiction where things could have been brought up in the examination but were not. This again would strain against well-established constitutional principles.

Conclusion

For all of the above reasons, I doubt it is worth the Government trying to legislate to create the proposed challenge window regime. The upside is extremely limited in practice. Even for a relatively simple case like Stonestreet Green, am I sure that if we’d gone through the challenge window process, we would have avoided a judicial review? I am not. There is a good chance the objectors would have drummed up other grounds after they had the final decision letter in their hands. Those grounds might well have been ‘totally without merit,’ but would have presumably taken at least the four months it took the actual Stonestreet Green judicial review to be determined. If so, the developer’s programme would have been longer overall if it opted into this new regime. For larger and more complex projects, the new regime is even less likely to deliver the intended objective.

In principle, you could achieve some of the same benefits, without the challenge window formalities, if the Secretary of State published the draft decision letter, draft DCO and PINS recommendation report for general comment in advance of making the actual decision. This would give the developer’s legal team (and the objectors) a chance to point out any manifest errors. However, overall I don’t favour this idea. It risks extending the three-month determination period for all DCO applications, while unearthing dangerous grounds on which a DCO might be quashed in only a tiny fraction. That doesn’t seem beneficial overall for UK infrastructure. 

For complex projects, where the Secretary of State is ‘minded to’ grant a DCO but with conditions that are worded significantly differently from those the developer proposed, there can be a benefit to sharing a ‘minded to’ decision letter in advance of publishing a final decision. This will give the developer an opportunity to point out practical impacts on viability and implementation, which may not be obvious to the Secretary of State’s team. This might extend the timeline for a decision, but will be worth it to prevent the unintended crippling of a project by civil servants. This is, however, an entirely separate objective to tackling judicial review risk.

I appreciate it is frustrating that there isn’t a legislative way to stop challenges being heard by the courts using a challenge window mechanism. However, this is no accident. Nor is it due to lack of legal creativity. The fundamental point is that it is the flip side of the robustness of our constitutional law: the separation of powers between the makers of our laws (Parliament) and the enforcers (the courts). Any reform that tries to oust the court’s jurisdiction to perform its constitutional role falls at that hurdle. The challenge window idea has a number of practical problems, which I have outlined, but the legal problems essentially come down to this. 

That is why my preferred solution to the problem of judicial review remains the provision of indemnities by Government to developers. These would largely mitigate the negative impact of judicial review (the reluctance of developers to commence works while a case is ongoing), while not giving rise to constitutional legal issues. Given that successful challenges to DCOs are so rare, and that even in successful cases the DCO will normally be granted on redetermination, pay outs by the Exchequer for abortive works would be few - and well worth it for the UK overall. It isn’t a perfect solution because injunctions might be granted by the courts to prevent developers from carrying out certain highly sensitive and irreversible works, or from compulsorily acquiring land, while a case is ongoing. But many developers will be able to plan a programme that works around these constraints. Certainly this idea, which was one of my main suggestions to the Nuclear Taskforce, is more powerful and realistic than any others I am aware of. I hope the Government expedites its implementation as widely as possible, and not just for the UK’s largest projects.

Many thanks to Harry Philpott KC for his review and endorsement of this article, and to the many others I have spoken to about these issues.