A runaway train was allowed to travel for four miles and go through four stations on the London underground.
The RMT union described the incident as a major failure in safety, claiming the runaway train had only narrowly missed a passenger on the Northern line at Archway.
As a result, passengers faced major delays on the Northern line. London underground staff quickly diverted passenger trains to the Bank branch, sending the runaway train through the Charing Cross branch.
London Underground issued a statement saying:
“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.”
However, Pat Sikorski, assistant general secretary of the RMT transport union, said: “We are appalled and horrified at this major incident during passenger traffic hours and which could have very easily resulted in disaster.”
London Underground have pledged a full investigation.