Campaigners trying to block Heathrow expansion have won a Court of Appeal challenge against controversial plans for a third runway.
A group of councils in London affected by the expansion, environmental charities including Greenpeace, Friends Of The Earth and Plan B, and London Mayor Sadiq Khan, brought legal action over the Government's approval of the plans.
Giving their ruling on Thursday, Lords Justice Lindblom, Singh and Haddon-Cave said the Government failed to take account of its commitment to the Paris Agreement on climate change when setting out its support for the airport expansion in its National Policy Statement.
The UN's Paris Agreement, which came into force in November 2016, commits signatories to tackling climate change by taking measures to limit global warming to well below 2C.
In a summary of the ruling, Lord Justice Lindblom told a packed court:
The judge said that, having seen the decision in advance, the Government did not oppose a declaration that the NPS was unlawful and had not sought permission to appeal to the Supreme Court.
Lawyers for the campaigners told the court at a hearing in October, when considering the proposals, that then-transport secretary Chris Grayling did not take enough account of environmental legislation or of climate change issues.
Prime Minister Boris Johnson opposed the expansion of the west London airport when he was London's mayor and promised to "lie down ... in front of those bulldozers" to stop the runway being built.
Earlier this month, he said there was "no immediate prospect" of construction beginning.
The coalition of councils, environmental campaigners and Mr Khan appealed against a High Court ruling in May, which rejected four separate judicial reviews of the Government's decision to approve the plans.
They argued that the Government's NPS setting out its support for the project failed to properly deal with the impact on air quality, climate change, noise and congestion.
Support from Labour MPs helped push through the proposals to expand Europe's busiest airport with an overwhelming majority of 296 in a Commons vote in June last year.
Mr Grayling said at the time that the new runway would set a "clear path to our future as a global nation in the post-Brexit world".
Heathrow says it could open the third runway "between early 2028 and late 2029". Its previous target date was 2026.
The airport said the delay was due to the Civil Aviation Authority, which refused to approve its bid to nearly quadruple the amount it spends before obtaining final planning permission.
Campaigners gathered outside court before the ruling, from 9am.