Heathrow expansion is “a fait accompli” and will be a “critical part of any new prime minister’s agenda”, the boss of the airport said.

Chief executive John Holland-Kaye refused to reveal when he last discussed the third runway with Tory leadership frontrunner Boris Johnson, but insisted the project “is now happening”.

Mr Johnson has previously voiced his opposition to expansion of the west London hub, declaring that he would lie in front of the bulldozers.

Asked if he believes Mr Johnson could be persuaded that a third runway should be built, Mr Holland-Kaye told PA: “It’s actually a fait accompli now. The vote in Parliament with nearly a four to one majority means this is now happening.

“The judicial review process was a resounding success for the Department for Transport at the first stage, so this is now a reality and things have moved on.

“We’re now making it happen."

Neil Lancefield is PA Transport Correspondent.