Plans to build a third runway at London’s Heathrow Airport were declared unlawful by a judge on Thursday throwing the future of the £14 billion project into doubt. The judge said the government’s plan had failed to take into account climate change commitments made by the UK when it signed up to the 2015 Paris Agreement. "That, in our view, is legally fatal” to the airport plan in its present form, said the judge, Keith Lindblom. The Conservative government had approved the project to increase the capacity of Europe’s busiest airport in 2018 but has been opposed by environmental campaigners and the country’s new prime minister Boris Johnson, who had vowed to lie down in front of bulldozers to halt the expansion plans. “Incredible news!” said environmental group Greenpeace in a tweet. “The third runway is already on its knees over costs, noise, air pollution and habitat loss.” Heathrow, which is owned by Ferrovial, Qatar Investment Authority and China Investment Corp, has claimed that the expansion of Heathrow is essential after Brexit as the UK seeks to expand its global trading networks. It said it would appeal against the ruling. Its two runways are currently operating at full capacity. The new runway was due to open in 2028 as it faces a challenge for the crown of Europe’s busiest airport from Charles de Gaulle airport in Paris, which has four runways. The ruling on Thursday does not rule out an eventual expansion but forces the government to review its airports policy. The government said it was a “private sector project” that would have to adhere to environmental requirements. Mr Johnson has repeatedly opposed the deal and had proposed a new island airport in the Thames Estuary, east of London, while he was the city’s mayor. When MPs voted to approve the Heathrow scheme, Mr Johnson travelled to Afghanistan in his former role as foreign secretary.