Proposals for London Britannia Airport, designed by architects Gensler, include four floating runways tethered to the sea bed.

The architect said the design allowed for future expansion to accommodate six runways when required.

Project director of the latest proposal Ian Mulcahey, said: “This will be a national infrastructure project that can inject new pace and dynamism into our economy.

“This isn’t a London airport, it is a global airport, designed, manufactured and built in the UK.”