Theresa May will allow ministers to express their opposition to airport expansion for a period of time after the decision is made next week, in the strongest signal yet that the government is preparing to back Heathrow’s bid to build a third runway.
The prime minister told colleagues at a Cabinet meeting yesterday that opponents of whatever decision was made would have a “set period” to speak frankly about their opposition.
Downing Street would not confirm whether that meant ministers would have a free vote in parliament to oppose the decision.
The Foreign Secretary, Boris Johnson, and the Education Secretary, Justine Greening, are vocal opponents of Heathrow expansion. Crucially, there are no London MPs on the cabinet sub-committee that will make the decision next week. The other two options under consideration are the extension of an existing runway at Heathrow, or the building of a second runway at Gatwick.
The committee members are: May; the Chancellor, Philip Hammond; the Business Secretary, Greg Clark; the Transport Secretary, Chris Grayling; the Communities Secretary, Sajid Javid; the Scottish Secretary, David Mundell; the Environment Secretary, Andrea Leadsom; the chief whip, Gavin Williamson; and the party chair, Patrick McLoughlin.
During Cabinet discussions, which lasted more than an hour, May told colleagues she expected any final scheme to be a “boost to business and competitiveness” and that the decision would be taken in the national interest. 
Her spokeswoman said: “The prime minister wanted to approach this in a mature way, recognising that a number of ministers have long held views on this issue. And in light of that there would be a certain period of time after the committee had taken its decision where they would be able to express those views and they would not be expected to publicly support the government’s decision.”
Downing Street said most cabinet members spoke during the meeting, but there was consensus that a decision needed to be made as soon as possible.
The spokeswoman hinted that ministers would eventually have to accept the government’s decision. “The decision will be subject to the ministerial code, in the usual way, including the rules of collective responsibility, but with this special arrangement for a limited time. She would not confirm if the period would cover the timescale for a vote in the Commons.
“Once a decision has been taken, certain ministers who have long-held views or particular constituency interests will have some flexibility to set out their personal position.”
No 10 said it was “not the expectation” that ministers would be able to actively campaign against the decision that was taken. Johnson has previously vowed to lie down in front of bulldozers if they started work on the third runway.