One of London's new £315,000 Routemaster buses broke down today on Tottenham Court Road.
Eye witnesses said the bus was there for up to an hour as it awaited repairs.
The vehicle was left stranded with its hazard lights on at the top of the busy high street near Warren Street Tube station at around 2pm today.
A police van blocked the street as the bus was towed a short distance by engineers, who started to examine it.
The bus was a number 38 which serves between Victoria Station and Hackney.
Earlier in the year, Transport for London (TfL) pledged that there would be eight in service on the route by the end of May.
The first of the new buses started service in February.
London Mayor Boris Johnson has pledged to have 600 of the three-door, rear-platform, driver and conductor buses on London streets by 2016.
Mike Weston, London Buses Director of Operations, said: “One of the prototype new bus for London vehicles has experienced mechanical problems this afternoon and engineers are investigating the cause of the fault.
"The bus was not in passenger service when the problem occurred and our team are working to return the bus to full operation as soon as possible.”
