Keep Chiswell Green v Secretary of State for Housing, Communities and Local Government & Ors
([2025] EWCA Civ 958)

Commentary: “No Automatic Procedural Bar, but a High Hurdle for Late-Arising Evidence in Planning Appeals”

1. Introduction

The Court of Appeal’s decision in Keep Chiswell Green addresses a familiar yet thorny question in planning law: after a public inquiry closes, what must the Secretary of State (or an inspector) do with new material that surfaces before the final decision? The case arose from two appeals—labelled Appeal A and Appeal B—relating to large residential schemes in the Metropolitan Green Belt at Chiswell Green, Hertfordshire. A residents’ group, Keep Chiswell Green (“KCG”), challenged the Secretary of State’s grant of permission, arguing that a fresh “Arup Green Belt Review” (“Arup Review”) published after the inquiry but before the decision was so obviously material that it had to be considered.

Lang J in the High Court rejected KCG’s challenge, invoking what she called a “preliminary procedural bar” derived from West and Mead: parties who withhold evidence at inquiry stage should not resurrect it later in court. On appeal, the Court of Appeal—Sir Geoffrey Vos MR, Laing LJ and Andrews LJ—agreed in outcome (the appeal failed) but emphatically disagreed with the notion of an absolute procedural bar. Instead, the Court reaffirmed that:

1. Late-arising matters can be mandatory material considerations, triggering the Secretary of State’s duty to consider them, but
2. They must pass the demanding Wednesbury “so obviously material” test, and the Arup Review did not.

2. Summary of the Judgment

• The Court dismissed both grounds of appeal.
• Ground 1 (Procedural Bar): The High Court had erred in treating the appellant’s silence as a categorical bar, but that error did not alter the result because the Arup Review failed the materiality test.
• Ground 2 (Mandatory Material Consideration): The Arup Review, being an early-stage local-plan evidence base, was not “so obviously material” to the Secretary of State’s task of determining whether “very special circumstances” existed to justify inappropriate Green Belt development. Hence, non-consideration was lawful.
• The Court clarified the interaction between Kides, Bath Society, Cumberlege, West and Mead, rejecting an “absolute rule” and articulating a fact-sensitive framework.

3. Analysis

3.1 Precedents Cited and Their Influence

R (Kides) v South Cambridgeshire DC [2002]

Established that a decision-maker must take account of any consideration that they actually know about and which is “obviously material”. The Court used Kides to frame the statutory duty under s 70(2) Town and Country Planning Act 1990.

The Bath Society [1991]

Held that an inspector’s failure to consider a local-plan inspector’s report (also post-inquiry) could invalidate a decision. Cited to show that non-party-raised matters can still be mandatory.

Baroness Cumberlege [2018]

Supplied the modern articulation of the “consistency” principle in planning decisions. Emphasised that knowledge and relevance determine whether non-consideration is irrational.

West v SSCLG [2005] & Mead [2024]

High Court authorities suggesting parties cannot spring new evidence on the court. The Court of Appeal distinguished them: they apply where the evidence existed during the inquiry, not where it emerges afterwards.

Friends of the Earth (Heathrow) [2020] UKSC 52

Supreme Court guidance on the three categories of considerations and the governing “Wednesbury” test. The Court imported this analytical structure wholesale.

3.2 Legal Reasoning

a) Statutory matrix. Sections 70(2) & 79(4) TCPA 1990 and s 38(6) PCPA 2004 require regard to “any other material considerations”. Rule 17(4) Inquiry Rules allows the Secretary of State to ignore post-inquiry representations unless they move him to disagree with the inspector (Dawes analogy).

b) Is there a procedural bar? No. The Court held that neither statute nor case law establishes a blanket prohibition on raising new matters. West/Mead concern fairness and efficiency; they do not oust jurisdiction. At most, the court has a remedial discretion.

c) The “so obviously material” test. Applying Friends of the Earth:

Result: non-consideration was not irrational; therefore, no breach of the statutory duty.

3.3 Likely Impact of the Judgment

1. Clarifies litigation strategy. Community groups may still challenge decisions on post-inquiry evidence, but they face a formidable materiality threshold.
2. Guidance for local authorities. Authorities commissioning new evidence must proactively flag genuinely game-changing documents; silence can imply lack of materiality.
3. Inspectorate practice. Inspectors/Secretary of State may confidently rely on Rule 17 discretion: only re-open if the new matter would alter the recommendation.
4. Judicial review boundaries. The Court emphasised that remedial discretion remains, but it is to be exercised case-by-case—not by erecting rigid procedural fences.
5. Green Belt jurisprudence. Confirms that broad “suitability for release” studies carry limited weight in development control decisions focused on very special circumstances.

4. Complex Concepts Simplified

Material Consideration

Any factor a planning decision-maker may lawfully take into account. If it is “obviously material” (i.e. no reasonable decision-maker could ignore it), failure to consider it is unlawful.

Very Special Circumstances (VSC)

Under National Planning Policy Framework para 152 ff., development in the Green Belt is inappropriate unless “other considerations” clearly outweigh Green-Belt harm. The bar is intentionally high.

Rule 17 Inquiry Rules 2000

Governs procedure after a planning inquiry closes. The Secretary of State may ignore late representations (r 17(4)) but must consult parties if he relies on them and alters the inspector’s recommendation (r 17(5)-(7)).

Sequential Test (context: Mead)

Policy requiring flood-prone developments to be permitted only if no safer sites are reasonably available. Mentioned to contrast factual settings.

Wednesbury Irrationality

A decision is irrational if it is so unreasonable that no reasonable authority could ever have taken it. Here applied to ascertain whether ignoring the Arup Review was lawful.

5. Conclusion

The Court of Appeal’s ruling threads the needle between procedural discipline and substantive fairness. It disapproves the idea that parties are forever silenced if they withhold late evidence, yet maintains a stringent “game-changer” test before the Secretary of State is obliged to engage with such evidence. For practitioners, the case is a timely reminder:

• If post-inquiry material truly undermines the inspector’s reasoning, raise it promptly—otherwise you risk both waiver and failure on the merits.
• High-level, untested studies that do not go to the heart of the site-specific planning balance will rarely be “mandatory” considerations.
• Courts will scrutinise both the decision-maker’s knowledge and the evidence’s inherent weight, not mere plausibility, when applying the Wednesbury test.

Ultimately, Keep Chiswell Green reinforces the primacy of focused, evidence-based inquiry hearings while keeping the door open—narrowly—for exceptional late-arising considerations.