Runaway train on London Tube's Northern Line

A runaway train went through six stops on a 13-minute journey on London's Tube as other trains were cleared out of its path.

The engineering train became uncoupled as it was towed on the Northern Line near Archway station on Friday morning.

Passenger trains were diverted to another branch of the Northern Line while trains were cleared from the Charing Cross branch.

The train ran for nearly four miles before it stopped at Warren Street.

Pat Sikorski, assistant general secretary of the Rail, Maritime and Transport union, said he was "horrified" as it could have "very easily resulted in disaster". He said the union understood a collision with a passenger train "was only narrowly avoided".

The incident caused disruption on the line for most of Friday morning.

Investigation launched London Underground (LU) said the engineering train, which was undertaking rail maintenance work, had been travelling southbound on the High Barnet branch of the Northern Line.

It became defective as it approached Archway, in north London, at about 0525 BST.

Engineers began to move the defective train northbound by coupling it to an out-of-service Northern Line train.

But at about 0644 BST, the engineering train, which does not carry passengers, became detached from the towing train and began to move southbound.

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We are appalled and horrified at this major incident during passenger traffic hours which could have very easily resulted in disaster”
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Pat Sikorski RMT spokesman

LU staff took the decision to divert passenger trains to the City branch while directing the engineering train to the cleared Charing Cross branch.

The engineering train came to a halt at Warren Street in central London at 0657 BST because the station is at the bottom of an incline.

A Transport for London (TfL) spokesman said: "A full investigation has been launched into this incident."

The line was suspended between Finchley Central and Archway and between Camden Town and Kennington via Charing Cross, leading to widespread disruption.

LU director Richard Parry said: "Safety is our top priority and we have, of course, launched an immediate and thorough investigation into this incident to establish the cause."

Mr Sikorski, from the RMT, said: "We are appalled and horrified at this major incident during passenger traffic hours which could have very easily resulted in disaster.

"The runaway train, which it is suspected broke loose from a failed emergency coupling, represents a safety failure of the highest order. We understand that a collision with a passenger service train leaving Archway was only narrowly avoided."

He added that the union was "seeking urgent answers" as to whether third party contractors were involved.