Tube line cleared as runaway London Underground train careers through stations

The unmanned engineering train, used for maintenance, began to move southbound from Archway station on the Northern line.

London Underground (LU) staff took an operational decision to let the train continue and diverted trains on to another branch of the Northern line while clearing trains from the Charing Cross branch on which the runaway train had been diverted.

The train eventually came to a stand at Warren Street station. LU and the Rail Accident Investigation Bureau have launched an investigation into the incident and LU has suspended the use of all similar trains.

LU said the train had become defective at 5.25am as it approached Archway. Engineers began to move the train away by coupling it to an out-of-service Northern line train.

LU went on: "However, for reasons that are now under investigation, at around 6.44am the engineering train became detached from the Northern line train and began to move southbound. LU staff undertook a swift assessment of the incident and an operational decision was made to allow the train to continue, until it came to a stand at Warren Street on the Charing Cross branch of the Northern line, which it did at 6.57am."

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.

"Once that investigation is complete, we will publish the report, making its conclusions and recommendations clear."