Proposals have been mooted to make the M25 a 16-lane motorway if Heathrow airport gets its contentious third runway.

Bosses in charge of the airport revealed plans to widen the stretch between Junctions 14 and 15 to accommodate the extra congestion the expansion would bring.

The suggestion was made in Heathrow’s final plan for the third runway, which was submitted to the Government.

Under the proposals the construction work on the motorway would take four years and be ready for 2021.