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41: New Welsh guidance, the use of AI in planning and other updates

Today’s entry looks at new consultation guidance in Wales, the use of AI in planning and a disclosure by the Secretary of State on carbon in judicial review proceedings.

Cymru Consultation

The Welsh Government has published guidance on pre-application consultation for the Significant Infrastructure Projects regime. In short, the new regime smells, walks and talks like the DCO regime with very important quirks, and given the new guidance, something which may reflect the pre-Planning and Infrastructure Act 2025-world.

Just as we are in the process of removing statutory consultation for DCO projects in England, the guidance document appears to be at risk of transposing the issues in Wales that led to that very same removal. The guidance document specifies that “it is generally advisable to undertake an iterative, multi-stage approach to consultation to enable communities to influence emerging plans from an early stage. The exact scale, overall programme and number of phases of consultation will be dependent on the scale and impact of each SIP application” and the guidance document appears to contemplate at least three stages of consultation and engagement.

On what should be included, this is a much more practical document about what the Welsh Government considers to be good consultation. It even suggests for the first stage of consultation that “a postcard can be a simple, cost effective way to introduce the proposal and give contact details and the website details”.  However, it lauds “high quality” information suggesting that the bar in England may need to be exceeded. One of the “measures of success” is the “number of substantive changes made to the project as a result of feedback” which may unintentionally encourage maximalist approaches and/or assume that substantive changes need to be met in relation to infrastructure which is of critical importance.

We are all waiting with bated breath for the DCO pre-application guidance, and it's hoped that it will definitively close the door on the open-ended approach taken to date. For those interested in the Welsh regime, you can read here and here.

Profound apologies

The Secretary of State for Transport has taken the atypical step in writing to the High Court as a result of data, provided in the judicial review proceedings of the Gatwick Airport DCO, containing a “small error.” In particular, emissions values reported were wrong, though that error amounts to “the headline difference between the average annual total aviation emission figures as provided to the Court and the corrected figures for the CB6 period is an increase of 4.1 MtCO2e over the 5-year Carbon Budget 6 period”.

The Secretary of State is clear that “this small error does not affect the decision I have taken" because "the information contained in the disclosed information was not material to the decision at the time, and even if it had been taken into account, it is highly likely the outcome of the decision would have been the same”. Judgment is awaited in the judicial review.

Unidentified Filed Objections (UFOs)

There are new advice notes, issued by the Planning Inspectorate, on producing application documents and separately making relevant representations. The former contains a new section on the “use of artificial intelligence”. In particular, it sets out that “Professional parties are responsible for ensuring their submissions are accurate and lawful. You may use artificial intelligence (AI) to help prepare information for the Planning Inspectorate, but you must tell us if AI has been used to create or significantly change any part of your submission. If you do not include as part of the submission a statement that you have used AI, the Examining Authority can reject the submission.”

The latter guidance document has been updated to include a reference to the “Use of artificial intelligence in casework evidence”, another piece of advice on the declarations required (including “What checks you  made and that you take responsibility for the accuracy of the content”).

That may not be sufficient to stop the tide of using artificial intelligence in the NSIP process, not least because some organisations are actively selling the idea of writing objections. I wonder whether a more robust approach to costs recovery may be more impactful in this context. That last document is clear that “improper use [of AI] could be at risk of being found as an example of unreasonable behaviour, and open to an award of costs.”

Interestingly, there is a (conventional) planning appeal decision where this issue was explored. The Inspector noted that one party’s submissions “ran to over 50 pages and raised 12 separate issues”. The Inspector’s eyebrows were clearly raised, and the decision notes:

“It is not just the detail, scope and lengthy citation of appeal decisions and case law that raises suspicion but also the unusual layout and phraseology. It is very different to anything I have encountered before. No author other than PK is identified, who as far as I am aware, is not a planning professional. One is therefore inevitably drawn to ask how PK could have produced such a document which would have been a significant undertaking even for the most experienced planning consultant”

In case you thought that was high praise, the Inspector concluded that they had “serious concerns that the [representation] was produced using AI, something which undeclared, would in my view amount to unreasonable behaviour as the Appellant was required to respond to the many points raised” In that case, there was no costs award simply because the Inspector chose to “exercise discretion and give the benefit of some substantial doubt” to the party.

Anyway, whilst we’re all waiting for Kang and Kodos to register as interested parties, you may want to read this procedural decision this week about document production more generally.

This publication is intended for general guidance and represents our understanding of the relevant law and practice as at March 2026. Specific advice should be sought for specific cases. For more information see our terms & conditions.

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Written by
Mustafa Latif-Aramesh
Date published
06 Mar 2026

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