Investigation into runaway tube train

An investigation has been launched into the runaway engineering train that become uncoupled on the Northern Line on Friday morning and rolled for almost four miles before halting at Warren Street.

London Underground and the Rail

Accident Investigation Bureau will be looking into the incident, which began at Archway station at around 5.25am on Friday when an engineering

train broke down and was attached an out-of-service Northern Line train to be moved away.  At around 6.44am, the defective train became detached

and began to move

southbound.

The runaway train was diverted down the

Charing Cross branch, and passenger services restricted to the Bank branch. The loose train

came to a halt at Warren Street station at 6.57am, although passenger services on the Charing Cross branch remained suspended for much of Friday morning.

"Safety is London Underground’s top priority, and we have of

course launched an immediate and thorough investigation into this

incident to establish the cause," said London Underground's director Richard Parry.

Some reports have suggested a collision with a passenger train at Archway station was only narrowly avoided on Friday morning. Overnight engineering works are currently managed by Tube Lines, and the investigation will examine the role of any private contractors in the incident.

The use of engineering trains of the design involved in Friday's events has been prohibited on the

Underground pending the findings of the investigation.