The Court of Appeal refused permission to appeal against the Gatwick northern-runway development consent on Tuesday morning, holding that every ground put forward was unarguable. Lord Justice Holgate and Lord Justice Dove handed down [2026] EWCA Civ 1040 at 10am, dismissing applications by the campaigner Peter Barclay and by Communities Against Gatwick Noise Emissions and finding that neither had a real prospect of success.

The two-day hearing on 27 and 28 July decided only whether an appeal could go ahead, not the appeal itself. Below, at a rolled-up hearing in June, Mr Justice Mould had granted permission on several of the grounds, heard them substantively and rejected them; Tuesday's ruling ends that route. The court certified that its decision may be cited as authority.

The climate arithmetic the consent rests on is set out at paragraph 71 of the judgment, and its provenance is worth stating precisely. The figure is Gatwick Airport Ltd's own assessment, recorded in the transport secretary's decision letter rather than found by any court: the airport put the carbon dioxide resulting from the proposed development at 6.344 million tonnes, or 0.657% of the emissions allowed under the UK's sixth carbon budget.

That percentage implies a sixth carbon budget of roughly 965 million tonnes, which is what the Carbon Budget Order sets for 2033 to 2037. But the numerator and the denominator are not measuring the same universe. The 6.344 million tonnes is the increase attributable to the development, and by the decision letter's own account it excludes inbound international flights, fuel produced outside the UK and non-carbon-dioxide effects. The budget it is compared against is a statutory cap on the whole UK economy, and aviation's warming effect is substantially non-carbon-dioxide.

The comparison is therefore narrower than it sounds in both directions at once — a partial measure of one airport's growth set against a total measure of a national budget — and it is the ratio on which a runway has now cleared its final legal obstacle.

A second figure in the judgment, 5.577 million tonnes or 0.578%, covers the aviation component alone. The two should not be run together: they answer different questions and imply different shares of the budget.