A double-decker bus crashed into a railway bridge, almost slicing off its roof, after the driver took a wrong turn.
The accident happened in Norbiton, south-west London, as the bus was travelling from Kingston to Tooting Broadway, Transport for London (TfL) said.
No passengers were on board at the time and the bridge was not damaged, meaning rail services were not affected.
A TfL spokesman said the accident was due to "human error" and that while the driver was not injured, he was "a bit shaken up".
Mike Weston, TfL's director of buses, said: "At around 13:00 an out-of-service route 131 double-decker bus, operated by London United, hit a rail bridge on Coombe Road near Norbiton station after taking a wrong turn.
"The bridge was not damaged and rail services are unaffected. There were no injuries and the incident will be fully investigated."