A runaway train on the London Underground went through six stops on a 13 minute journey, with other trains having to be cleared out of its path.
The engineering train, which was undertaking rail maintenance work,
became uncoupled as it was towed on the Northern Line on Friday morning.
The BBC reports it ran for more than 6km before coming to a stop at Warren Street on a slight incline on the track.
Passenger trains were diverted to another branch of the Northern Line while trains were cleared from the Charing Cross branch.
An official from the Rail, Maritime & Transport Union says he understands a collision with a passenger train was only narrowly avoided.