Barclay & Anor v Secretary of State for Transport

Factual and Procedural Background

On 21 September 2025, the First Respondent made a development consent order authorising improvements to the northern runway at Gatwick Airport, the lifting of restrictions so that the northern and southern runways could operate as dual runways, and related airport and surface-access development. [Para 59]

The First Appellant and the Second Appellant brought judicial review claims against that order under section 118 of the Planning Act 2008, with the Second Respondent participating as an interested party. Mould J heard the permission applications on a rolled-up basis, granted and refused permission on different grounds for each appellant, and dismissed both claims. [Para 60][Para 61][Para 62]

The Court of Appeal heard the two permission-to-appeal applications together on 27 and 28 July 2026. [Para 63]

Legal Issues Presented

1. Whether the Airports National Policy Statement and the “Making Best Use of Existing Runways” policy supported the development consent order for Gatwick Airport expansion, or instead required that such development be treated as outside the policy framework. [Para 77][Para 78][Para 79][Para 107][Para 114]
2. Whether the First Respondent irrationally relied on the Second Respondent’s National Economic Impact Assessment or business passenger forecasts, or failed to give adequate reasons on need and economic benefit. [Para 81][Para 82][Para 134][Para 144]
3. Whether the treatment of greenhouse gas emissions, including non-CO2 emissions, was irrational or contrary to the Environmental Impact Assessment regime and the Airports National Policy Statement. [Para 89][Para 90][Para 153][Para 180][Para 223]
4. Whether the Jet Zero Strategy and later policy material were lawfully relied on, including whether the First Respondent needed to take account of later delivery-risk information. [Para 91][Para 264][Para 278]
5. Whether the wastewater requirement in the order, including its “tailpiece,” was lawful. [Para 93][Para 282][Para 309]

Arguments of the Parties

First Appellant's Arguments

• The First Appellant argued that the policy in the Airports National Policy Statement did not support expansion of capacity at Gatwick Airport, or at least not expansion on the scale proposed, and that any such proposal should have been treated as a departure from policy. [Para 77][Para 78][Para 79][Para 97]
• The First Appellant also argued that the First Respondent irrationally accepted national economic benefits without properly grappling with the Second Respondent’s National Economic Impact Assessment and the criticism made of its business passenger forecasts. [Para 81][Para 82][Para 134]
• It was submitted that the First Respondent’s reasons were inadequate and contained gaps in logic. [Para 83]
• The First Appellant maintained that each ground had a real prospect of success or otherwise justified permission to appeal. [Para 84]

Second Appellant's Arguments

• The Second Appellant contended that the First Respondent took an irrational approach to greenhouse gas significance because she described the effects as “moderate significant adverse” while also concluding that the project would not materially affect the Government’s ability to meet net zero targets. [Para 89]
• It argued that non-CO2 emissions required a quantified assessment and that the absence of such an assessment breached the Environmental Impact Assessment duties and the precautionary principle. [Para 90][Para 194][Para 195]
• It contended that the First Respondent failed to take account of material risks to delivery of the Jet Zero Strategy, or failed to make proper enquiries about them, and that she gave the Strategy too much weight. [Para 91][Para 263][Para 268]
• It argued that the wastewater requirement should have required the alternative treatment works to be operational and used, and that the tailpiece was unlawful. [Para 93][Para 305][Para 307]
• The Second Appellant likewise submitted that its grounds had a real prospect of success or compelling reasons existed for permission to appeal. [Para 94]

Table of Precedents Cited

Court's Reasoning and Analysis

On the planning-policy issue, the court held that the Airports National Policy Statement and the Making Best Use policy had to be read as a whole and in context. They supported more intensive use of existing airports beyond Heathrow, including Gatwick, provided the proposal demonstrated a need additional to or different from the need met by Heathrow’s Northwest Runway and addressed environmental concerns. [Para 100][Para 102][Para 106][Para 107][Para 108][Para 109][Para 110][Para 112][Para 115][Para 116][Para 124][Para 125][Para 126][Para 127]

The court rejected the First Appellant’s attempt to treat references in the policy to “more intensive use of existing airports other than Heathrow and Gatwick” as excluding Gatwick expansion, holding that this language described the wider context of airport capacity constraints and did not impose a cap on scale. [Para 113][Para 126][Para 127]

On the economic-benefits ground, the court found that neither the Examining Authority nor the First Respondent relied on the National Economic Impact Assessment or any estimate of business-passenger growth as the foundation for their conclusions. Instead, they relied on the different market roles of Gatwick and Heathrow and on wider evidence of need and socio-economic benefit. [Para 138][Para 140][Para 143][Para 144][Para 145][Para 146]

On greenhouse-gas significance, the court held that the First Respondent was entitled to distinguish between the IEMA guidance on significance and the policy test in paragraph 5.82 of the Airports National Policy Statement. A project could fall short of fully contributing to net zero without that necessarily making it so significant as to materially impede the Government’s carbon targets. [Para 153][Para 160][Para 165][Para 171][Para 172][Para 179][Para 180][Para 181]

The court also held that the First Respondent lawfully accepted a qualitative rather than quantitative approach to non-CO2 emissions because the Examining Authority had identified methodological uncertainty, later material did not show that uncertainty had been resolved, and the precautionary principle did not require a different answer. [Para 203][Para 206][Para 208][Para 214][Para 215][Para 221][Para 222][Para 223]

On the Jet Zero Strategy challenge, the court held that the First Respondent was entitled to rely on her own climate policies, including the Jet Zero Strategy’s High-ambition scenario, and to treat later monitoring material as consistent with a system of review and adjustment rather than as undermining the policy. [Para 237][Para 242][Para 246][Para 247][Para 250][Para 251][Para 254][Para 255][Para 256][Para 262][Para 277][Para 278]

On the wastewater condition, the court held that the First Respondent was entitled to assume that the relevant authorities and the operator would act rationally, and that the requirement adequately addressed the risk of wastewater flows. The tailpiece was lawful because it only allowed an alternative means of achieving the same required wastewater treatment outcome, not materially different development. [Para 296][Para 302][Para 304][Para 306][Para 309]

Holding and Implications

Permission to appeal was refused on every ground, because each proposed appeal was held to be unarguable and there were no other compelling reasons to hear either appeal. [Para 131][Para 148][Para 188][Para 224][Para 279][Para 310][Para 312]

The direct consequence was that both appellants’ challenges failed, the development consent order remained in force, and the court certified that the decision may be cited as authority. No broader new precedent was stated beyond the application of existing planning, EIA, and climate-policy principles to these facts. [Para 312]