Expansion at Heathrow is "deliverable but only with political will" - clear government leadership and decision now needed, says former transport minister Lord Andrew Adonis.

Sir Howard Davies "clear and unambiguous" recommendation in favour of developing Heathrow, explained former transport minister Lord Adonis. However, to turn this into a reality, Prime Minister David Cameron would have to "eat his words" and make a decision in favour of making it happen.

"Howard Davies makes a very clear and unambiguous recommendation in favour of developing Heathrow," he said. "What is needed now if government to take a decision - but it would involve David Cameron to some extent eating his words - he will need to argue convincingly that this is a new scheme and different from plans dismissed five years ago."

"It is perfectly possible for the government to do nothing - but do nothing under the guise of activity" Lord Adonis

Speaking at the Runways UK conference this week, Adonis emphasised that the Heathrow expansion project was politically viable as it had wide support from politicians and local residents. But it would, he added, require some use of political capital at a moment when he had many other things on his plate.

"I would say it is 50:50 at the monent as to whether Heathrow goes ahead," he added. "David Cameron has a Euro Referendum and a London Mayoral election to deal with next May so has significant problems within his own party. While I'm sure George Osborne would like to proceded, David Cameron has never been wildly in favour of Heathrow and aviation in the past."

He added: "The question is whether the political will is there and we wont know that until the Autumn. It does rely on a firm lead by the government. 

"It is perfectly possible for the government to do nothing - but do nothing under the guise of activity by setting up a further review for example - that could easily last another year. But it is very unlikely the government will simply kill the scheme."