A new runway at Heathrow Airport might be built over the M25, the Transport Secretary has said.
Chris Grayling's comments follow Tuesday's announcement that the government has chosen Heathrow as its preferred airport expansion project.
Speaking on BBC Radio 4's Today programme, Mr Grayling said: "One of the things that Heathrow has been looking at is doing what many other airports have done around the world - which is to build their runway over the top of the road rather than tunnelling the road underneath it.
"It is a cheaper and quicker way of doing it. I am, of course, very concerned to make sure that, as this runway is built, it doesn't cause massive disruption on the M25, so I think this is a sensible way.
"It is a very gentle hill up which the planes would take off rather than a flat surface. It's what happens at very many airports around the world."
Tory MPs are taking lumps out of each other on Heathrow, grammar schools and - above all - the true meaning of Brexit.
Environmentalist Goldsmith called the move "catastrophic" - and announced he will now stand as an independent in protest.
The expansion of the London airport will affect the whole of the UK, with more domestic routes, while impacting air fares and house prices.