An alien metropolis or the solution to London's transport problems? Architects unveil futuristic plans for 'Boris Island' airport in Thames Estuary

 The London Britannia Airport, designed by architects Gensler, includes four floating runways tethered to the sea bed. Gensler says new runways could be floated in as required - allowing for future expansion to accommodate six landing strips. Passengers would check in and arrive at terminals on the land.