ANPS “Material Impact” Net Zero Test Is Distinct from IEMA GHG Significance Ratings: Reliance on Jet Zero Strategy, Qualitative Non‑CO₂ EIA, and Constrained “Otherwise Agreed” DCO Requirements

1) Introduction

In Barclay & Anor v Secretary of State for Transport [2026] EWCA Civ 1040, the Court of Appeal (Holgate LJ and Dove LJ) refused permission to appeal from the Planning Court’s dismissal/refusal of permission in two judicial review challenges under s.118 Planning Act 2008 to a development consent order (“DCO”) authorising works at Gatwick Airport enabling dual runway operations and associated development (terminals, hotels, offices, car parking and surface access).

The appellants were (i) the first appellant (an individual claimant) and (ii) Communities against Gatwick Noise Emissions (CAGNE). The decision-maker was the Secretary of State for Transport (“SST”), with Gatwick Airport Limited (“GAL”) participating as interested party/second respondent.

Although procedurally this was a permission-to-appeal decision, the judgment contains substantial treatment of recurring issues in nationally significant infrastructure project (“NSIP”) litigation: interpretation of the Airports National Policy Statement (“ANPS”) alongside “Making Best Use of Existing Runways” (“MBU”); the relationship between professional “significance” guidance for greenhouse gases (“GHGs”) and ANPS policy tests; the standard of review for EIA methodological choices (including non‑CO2 effects); reliance on the Jet Zero Strategy (“JZS”) in the context of the Climate Change Act 2008; and the legality of DCO “requirements” containing “unless otherwise agreed” tailpieces.

2) Summary of the Judgment

  • All grounds were “unarguable”; neither appeal had a real prospect of success and there were no other compelling reasons to hear them ([98]).
  • ANPS/MBU interpretation: it was not arguable that ANPS policy was hostile to, or capped, “making best use” expansion at Gatwick; the SST and Examining Authority (“ExA”) interpreted ANPS/MBU correctly ([15]–[26]).
  • Economics/need: the SST did not rely on GAL’s National Economic Impact Assessment (“NEIA”) or business-passenger benefit estimates; therefore alleged flaws in that material did not create a reasoning gap or irrationality ([27]–[34]).
  • GHG significance vs ANPS 5.82: there was no contradiction between finding a “moderate significant adverse” effect under IEMA guidance and concluding (under ANPS [5.82]) no “material impact” on the Government’s ability to meet net zero/carbon budgets; those are different evaluative questions ([35]–[50]).
  • Non‑CO2 emissions: it was not arguably irrational to accept a qualitative assessment given methodological uncertainty; the EIA Regulations do not mandate quantification in these circumstances, and the precautionary principle did not compel a different outcome ([51]–[69]).
  • JZS delivery risk / Tameside / Policy Commission return: the SST was entitled to rely on JZS/JZS:OYO and the Climate Change Act 2008 monitoring architecture; it was not arguable that she had to obtain or consider a non-statutory “Policy Commission return” or that failure to do so was irrational or a breach of the Tameside duty ([70]–[90]).
  • Wastewater requirement: the requirement was not irrational; “unless otherwise agreed” wording was lawful, distinguishable from R (Midcounties Co-operative Limited) v Wyre Forest District Council [2009] EWHC 964, and constrained by a general DCO requirement preventing materially new/different environmental effects ([91]–[97]).
  • The Court certified the decision may be cited as an authority under the Practice Direction (Citation of Authorities) ([98]).

3) Analysis

A. Precedents Cited (and How They Shaped the Decision)

1) Interpreting policy: ordinary meaning, context, and “not like a statute”

The Court reaffirmed familiar principles from Tesco Stores Ltd v Dundee City Council [2012] UKSC 13; [2012] PTSR 983 and Hopkins Homes Ltd v Secretary of State for Communities and Local Government [2017] UKSC 37; [2017] 1 WLR 1865:

  • Policy interpretation is a question of law, but policy is drafted for practical decision-taking by specialists and the public.
  • Policy must be read as a whole and in its proper context; apparent tensions may reflect legitimate balancing.
  • Courts must distinguish “what the policy means” from “how it is applied and weighed” (primarily for the decision-maker, subject to public law controls).

These principles underpinned the rejection of the first appellant’s attempt to recast ANPS/MBU as implicitly excluding (or strictly limiting) Gatwick “making best use” expansion.

2) EIA adequacy and evaluative judgment (Wednesbury review)

On challenges to the content/method of EIA, the Court relied on the line of authority emphasising evaluative judgment and a high threshold for intervention: R (Suffolk Energy Action Solutions) v Secretary of State for Energy Security and Net Zero [2023] EWHC 1796 (Admin), R (Friends of the Earth Limited) v Heathrow Airport Limited [2020] UKSC 52; [2021] PTSR 190, R (Finch) v Surrey County Council [2024] UKSC 20; [2024] PTSR 988, and Boswell v Secretary of State for Energy Security and Net Zero [2025] EWCA Civ 669 ([56]).

This framing was decisive for CAGNE’s non‑CO2 ground: even if quantification methodologies exist in some settings, it was for the SST to judge adequacy “in an appropriate manner” under the EIA regime, and only irrationality would suffice.

3) The precautionary principle: demanding, but not outcome-determinative

The Court cited R (Wyatt) v Fareham Borough Council [2022] EWCA Civ 983; [2023] PTSR 1952 as approved in C.G. Fry and Son Limited v Secretary of State for Housing, Communities and Local Government [2025] UKSC 35; [2025] PTSR 1823 ([57]).

Even assuming the precautionary principle had relevance outside the Habitats Regulations context where it is most developed, it did not convert methodological uncertainty into a legal requirement to quantify non‑CO2 impacts here; application ultimately remains a matter of judgment for the decision-maker.

4) Reliance on climate policy (JZS) within the Climate Change Act 2008 architecture

The Court treated R (Dawes) v Secretary of State for Transport [2023] EWHC 2352 (Admin) as strongly supportive of the SST’s approach ([82]): decision-makers may rely on their own multi-faceted climate/aviation policies (including JZS) designed to deliver carbon budgets and net zero, without thereby precluding airport expansion.

That logic underpinned rejection of CAGNE’s “delivery risk” / “full weight” complaint.

5) Policy Commission returns: status and justiciability limits

On the “Policy Commission return” issue, the Court drew on R (Friends of the Earth Limited) v Secretary of State for Energy Security and Net Zero [2024] EWHC 995 (Admin); [2024] PTSR 1293 and R (Global Feedback Limited v Secretary of State for the Environment [2023] EWCA Civ 1549; [2024] 1 WLR 2923 to describe such returns as part of a non-statutory, internal, quarterly information process enabling the Government to discharge s.13 Climate Change Act 2008 duties ([86]–[88]).

The Court refused to treat that internal monitoring as something the SST must chase and integrate into each DCO decision on pain of irrationality—otherwise decision-making would become hostage to an evolving sequence of internal returns ([88]).

6) “Unless otherwise agreed” tailpieces in requirements

CAGNE’s reliance on R (Midcounties Co-operative Limited) v Wyre Forest District Council [2009] EWHC 964 was rejected because the “tailpiece” here operated within (i) the purpose and structure of the requirement and (ii) an additional control: DCO requirement 1(4), preventing “otherwise agreed” departures that would cause materially new/different environmental effects ([96]–[97]).

B. Legal Reasoning

1) ANPS and MBU: support for “making best use” is not excluded for Gatwick

The Court’s reading of ANPS [1.40]–[1.42] and MBU [1.29] was straightforward: ANPS is primarily about Heathrow NWR, but it expressly anticipates that airports beyond Heathrow may demonstrate “sufficient need” for “more intensive use” proposals, provided need is “additional to (or different from)” NWR ([17]–[23]).

The Court rejected attempts to treat ANPS statements about needing more intensive use of airports “other than Heathrow and Gatwick” (e.g. [1.6], [2.28]) as a prohibition on Gatwick expansion; those passages were contextual descriptions of capacity constraints, not an implied exclusion—especially when set against the express supportive language in ANPS [1.42] and MBU [1.29] ([24]).

Two further points were legally important:

  • No “scale cap” exists in ANPS/MBU on making-best-use proposals; NSIP thresholds (e.g. >10mppa) are expressly contemplated ([19], [24]).
  • Heathrow hub status was treated as a relevant consideration, but the ExA/SST conclusions that any diversion effects would be short-term and not unduly affect hub status long-term were a matter of planning judgment ([20]–[25]).

2) Economic benefits and reasons: no duty to resolve disputes about evidence not relied on

The first appellant attempted to build a reasons/irrationality challenge around criticisms (from NEF) of GAL’s NEIA, especially business-passenger assumptions. The Court held the challenge collapsed at the factual premise: the SST’s need and socio-economic conclusions were not materially founded on NEIA/business-passenger growth estimates ([31]–[34]).

The reasoning is notable for its administrative-law discipline: if a document is in the evidential “background” but is not used as a basis for the key conclusion, the decision-maker is not generally required to adjudicate technical disputes about it, nor to give reasons resolving them, unless it is a principal controversial issue material to the decision actually taken ([34]).

3) GHG “significance” (IEMA) versus ANPS [5.82]: different evaluative questions

CAGNE’s Ground 1 tried to turn an asserted inconsistency into irrationality: if emissions are “moderate significant adverse” under IEMA, how can the project be said not to “materially impact” the Government’s ability to meet net zero/carbon budgets under ANPS [5.82]?

The Court answered by separating the tools and the test:

  • IEMA guidance assists practitioners with “likely significant environmental effects” in EIA across project types; it is not drafted to apply ANPS policy tests ([37]).
  • The ANPS [5.82] question is whether effects are “so significant” that they would have a “material impact” on national target compliance—again a matter of degree and judgment ([46]).
  • It is logically possible (indeed common in impact assessment) for a project to fall short of “full contribution” to net zero and yet not be of such scale as to materially affect the national ability to meet budgets, particularly where policy frameworks aim to manage sectoral emissions over time ([46]).

The Court also rejected an attempted analogy with Boswell v Secretary of State for Energy Security and Net Zero [2025] EWCA Civ 669, emphasising that Boswell turned on whether IEMA had been applied at all, and in any event concerned different policy architecture and reasoning ([47]–[50]).

4) Non‑CO2 aviation impacts: qualitative assessment can be lawful and rational

CAGNE’s Ground 3 pressed for quantification of non‑CO2 impacts, pointing to multipliers used in other contexts and later materials (CCC advice; EU ETS monitoring changes). The Court accepted the legal framing: under the EIA Regulations, the SST must reach a reasoned conclusion on likely significant environmental effects (reg.21), but the adequacy of information/method remains evaluative and reviewable only on Wednesbury grounds ([55]–[56]).

Key reasons the qualitative approach survived:

  • The ExA found no agreed multiplier and too many uncertainties for plausible quantified outcomes; qualitative treatment captured the direction of effect (net warming) and its additional negative magnitude ([61]).
  • CAGNE itself had accepted at consultation stage that the ExA’s qualitative approach was lawful “at the time of Examination” ([62]).
  • The post-examination materials did not demonstrate that methodological concerns had been overcome such that refusal to quantify became irrational ([66], [68]).
  • The SST did not ignore non‑CO2 impacts; she treated them as an additional negative effect but considered policy/plan commitments to monitor and respond as policy evolved ([67]).

5) JZS delivery risk, Tameside, and internal monitoring documents

CAGNE’s Ground 4 argued the SST either failed to consider, failed to inquire about, or irrationally discounted risks to JZS delivery, relying particularly on (i) revised JZS:OYO modelling and (ii) a DfT “Policy Commission return”.

The Court disposed of (i) as already before the ExA/SST ([85]). For (ii), the Court’s reasoning is significant:

  • Policy Commission returns are part of a non-statutory, iterative governmental monitoring process supporting s.13 Climate Change Act 2008 duties; they are not sector targets and are designed to be updated as evidence changes ([86]–[88]).
  • It was not arguable that rational reliance on JZS mechanisms for monitoring/revision required the SST also to incorporate a specific quarterly return—still less a “whole sequence” of them—into the DCO decision ([88]).
  • Any argument that the return revealed decisive aviation-specific implications dissolved into technical dispute unsuitable for resolution on JR/appeal, and in any event did not demonstrate irrationality in the SST’s reliance on policy architecture (reinforced by Dawes) ([89]).

6) Wastewater “requirement 31”: operationalisation, permits, and tailpieces

CAGNE’s Ground 7 argued the DCO unlawfully allowed dual runway operations once an on-site wastewater treatment works (Work No 44) was merely “completed” and a permit application submitted—without requiring the works to be operational, a permit granted, or mandating its use; and that “unless otherwise agreed” could sidestep controls.

The Court endorsed the Planning Court’s view that these fears were “farfetched” and the SST could assume rational conduct by GAL/TWUL/EA, particularly given the regulatory context and the commercial reality of building expensive infrastructure without using it ([95]).

On legality, the “tailpiece” was distinguished from Midcounties because any alternative agreement had to operate within the objective of ensuring adequate wastewater treatment, and was additionally constrained by DCO requirement 1(4) prohibiting “otherwise agreed” departures causing materially new/different environmental effects ([97]).

C. Impact

1) Airports and ANPS/MBU: fewer footholds for “implicit exclusion” arguments

The judgment strengthens the proposition that ANPS/MBU, read as a whole, positively contemplates “making best use” proposals at airports beyond Heathrow (including in the South East), with the key policy discipline being “additional/different need” rather than an implied Gatwick carve-out or a de facto second-runway scale cap.

2) Climate challenges: separating EIA significance frameworks from policy thresholds

For climate-related JR claims, a clear analytical separation is reinforced: professional “significance” gradings (e.g. IEMA major/moderate/minor) do not automatically determine policy tests framed in different terms (e.g. ANPS [5.82] “so significant”/“material impact” on national target compliance). Claimants will need to engage with the specific policy language and the decision-maker’s evaluative judgment, not merely assert contradiction.

3) Non‑CO2 assessment: methodological disputes will rarely clear irrationality

Given acknowledged uncertainty, the Court’s approach signals that pushing a quantified non‑CO2 methodology will generally require showing not merely that a method exists, but that refusal to use it was irrational in context—especially where ExA/SST explain plausibility concerns and still assess the effect qualitatively as adverse.

4) Internal government monitoring documents: limits on “Tameside” expansion

The reasoning on Policy Commission returns suggests courts will be slow to treat evolving internal monitoring materials as mandatory considerations in individual planning decisions, particularly where the relevant strategy itself contains monitoring/review mechanisms and sits within the Climate Change Act 2008 architecture.

5) Drafting and defending DCO requirements

The decision provides a practical route to defending “unless otherwise agreed” language: (i) construe it purposively in the context of the requirement; and (ii) anchor it with a general anti-drift provision (here, requirement 1(4)) preventing materially new/different environmental effects. This may reduce vulnerability to Midcounties-style objections.

4) Complex Concepts Simplified

  • DCO / NSIP: a Development Consent Order is the statutory consent for nationally significant infrastructure under the Planning Act 2008, typically following examination by an ExA and decision by the SST.
  • ANPS / MBU: the Airports National Policy Statement sets national policy (principally for Heathrow NWR) but is “important and relevant” for other airport schemes; MBU is a policy statement supporting more intensive use of existing runways, subject to merits and environmental/economic considerations.
  • EIA “significance”: in Environmental Impact Assessment, “significance” concerns whether effects are likely significant for assessment/reporting; professional guidance (e.g. IEMA) helps structure that judgment.
  • ANPS [5.82] test: a separate planning-policy judgment about whether emissions effects are so significant that they materially impact the Government’s ability to meet carbon budgets/net zero.
  • Non‑CO2 aviation effects: impacts beyond carbon dioxide (e.g. contrails, NOx-related effects) with uncertain quantification; decision-makers may still assess them qualitatively as adverse.
  • Wednesbury irrationality: a high bar; the court intervenes only if a judgment is outside the range of reasonable responses.
  • Tameside duty: a duty to make reasonable inquiries where necessary to take a lawful decision; its content depends on context and materiality.
  • “Otherwise agreed” tailpiece: drafting that allows an approving body to accept alternatives; it is lawful where confined to the requirement’s purpose and not used to bypass the statutory process or introduce materially different effects.

5) Conclusion

The Court of Appeal’s refusal of permission in [2026] EWCA Civ 1040 consolidates several practical public-law messages in NSIP litigation: (i) ANPS/MBU policy is not to be rewritten to create implied exclusions or scale caps unsupported by text; (ii) technical disputes about materials not relied upon will not readily generate reasons/irrationality errors; (iii) IEMA “significance” categories do not dictate ANPS [5.82] “material impact” judgments; (iv) qualitative treatment of non‑CO2 emissions can be lawful where quantification remains uncertain; (v) the JZS and the Climate Change Act 2008 monitoring architecture provide a defensible foundation for evaluating emissions; and (vi) “unless otherwise agreed” DCO drafting is sustainable where constrained to avoid materially new or different environmental effects.