Heatherwick Studio has been working with Wrightbus and Transport for London to realise the design since January.
The consultancy was brought on the project after an initial competition selected a concept by Capoco Design and a collaborative entry by Foster & Partners and Aston Martin in 2008.
Set to launch in 2012, the new bus features an open boarding platform and interior decking, taking inspiration from the old Routemaster.
Two staircases are built in – the rear is encased with a window that follows the contour of the stairwell.
The mock-up will be used to ‘fine-tune the design’, Transport for London says, and Johnson explains that the bus ‘brings back a sense of nostalgia, but conversely also demonstrates the quintessence of the latest technology and design’.
It is claimed that the design is 15 per cent more efficient than existing hybrid buses and 40 per cent more efficient than conventional diesel double-deckers.