A court judgment that plans to expand Heathrow were made illegally has been branded a “major breakthrough” for efforts to tackle climate change.

Environmental campaigners, the mayor of London and a group of west London councils have fought long and hard against the government’s decision to build a third runway at Heathrow, set out in a national policy statement on aviation in 2018. They argued that expansion would violate the UK’s international climate commitments under the Paris Agreement, increase local air pollution and noise, and harm biodiversity.