Ian Prosser, Director of Safety for the Office of Rail Regulation, said:
“London Underground is one of the safest railways in the world and normally has a very good safety record. The companies responsible for running and maintaining services have an important duty to ensure that their workers and members of the public are not exposed to unnecessary safety risks.
"However, in this case, London Underground, Tube Lines and Schweerbau, through inadequate management and planning, failed to ensure the safe recovery of an engineering train. This is clearly unacceptable, and led to a potentially catastrophic incident on the Northern Line where the train careered out of control for over four miles. It was only the professionalism of control room staff taking decisive action which prevented a collision between trains, and averted a much more serious outcome.
"We welcome the steps taken by the companies to improve safety management on London Underground since this incident. The regulator will continue to closely monitor the actions of all parties involved, and will not hesitate to step in should further safety failings be found."
More top news
A lamp in the tower which houses Big Ben is to be switched off for the first time in more than 70 years.
Sir Bruce entertained audiences for more than seven decades.
Work in the tower will also pause over the bank holiday weekend.