Night buses aren't generally scary places: they might be full of guilt, or tinged with embarrassment, but they're not really frightening.
Not so, the phantom Number 7, haunting the roads around Cambridge Gardens in Ladbroke Grove, west London.
Last seen as recently as 1990 (1990!), the spooky apparition first came to fame in the 1930s, when it caused a significant road accident.
Late one night, a motorist driving along Cambridge Gardens suddenly swerved for no apparent reason. Sources differ as to what happened next.
Some say his car hit a wall and burst into flames, killing the unfortunate soul inside. It was at the inquest into his death that witnesses came forward, saying they'd seen a ghostly, unlit, driverless bus speeding down the centre of the road and that had caused the chap to crash.
Another version of events has the driver escaping — unhurt — and giving an eyewitness account: he told the police a bright red Number 7 double-decker had been hurtling towards him, forcing him off the road. In this account, the bus's lights are on, but there's no driver or passengers at home... spooky.
The authorities set out to find this rogue vehicle, but found no buses scheduled in that area, or the surrounding streets at all.
(Night buses were first introduced in London in 1913, but they were few and far between in the 1930s.)
Then more accidents started happening. Always at the same time (1.15am) and always at the same place on Cambridge Gardens.
Eyewitness accounts were remarkably similar: a speeding double-decker had forced a car off the road; when the startled drivers turned around to see the out-of-control, driverless bus, there was nothing there.
Whatever it was had vanished without trace.
Check out our video on London's weirdest ghost stories, which features the phantom double-decker: