The mayor of London has switched his allegiance away from a so-called Boris Island hub in the Thames estuary in favour of a four-runway airport on the Isle of Grain in north Kent.

Boris Johnson admitted that his original idea for an alternative to Heathrow in the outer estuary would be too far from the centre of London.

The £65 billion lsle of Grain option, originally put forward by architect Lord Foster, would eventually be able to handle 180 million passengers a year by 2050 with a new train line taking travellers from Waterloo within 26 minutes.

The first stage of the project would open in 2029 and initially handle 90 million passengers at a cost of £20 billion financed by private investors.

The idea is one of three Johnson will submit to the government’s Airports Commission together with expanding Stansted into a four-runway airport with improved rail links.

Heathrow would be acquired for about £15 billion and be converted into a new town with up to 200,000 homes.

Johnson’s about turn comes as Heathrow’s owners are expected to put forward plans for a third and possibly fourth runway at the west London airport, with at least three options likely to be flagged up to the Airports Commission.

The mayor told the Sunday Times his new hub would “knock the spots off” rival airports in Paris, Frankfurt and Amsterdam and make the UK the “global capital” of aviation.

“It would cement London’s position as the number one economic commercial powerhouse of Europe, if not the world,” he said.

But expanding Heathrow would be a “catastrophic and economic mistake,” according to Johnson.