Video showing how close a runaway London Underground train was to a full passenger train in front of it has been leaked to BBC London.
The footage of a control room monitor appears to show the runaway engineering train close behind the other vehicle as they pass Kentish Town.
A highly-placed source said the two trains were just 49 seconds apart during the incident on Friday morning.
Transport for London has said safety is its top priority.
The engineering train went through six stops on its 13-minute, four mile journey after becoming detached on the Northern Line.
Other trains were cleared out of its path, while passengers travelling in the train ahead were told to go to the front of the vehicle.
An incline in the track finally brought the engineering train to a halt.
Now BBC London has been told the vehicle had no brakes.
And a leaked report reveals the driver of the engineering train jumped clear at Highgate Tube, while a platform at Camden Town station was evacuated.
A full investigation has already been launched into the incident.
The Rail Accident Investigation Bureau (RAIB) said it could not say how long it expected the investigation to take.
A TfL spokesman said: "Safety is our top priority and the events surrounding the incident last Friday remain under investigation.
"We would not wish to pre-empt the outcome of our investigation but once all of the facts have been verified we will publish the report, making all of its conclusions clear.
"We once again pay tribute to our quick-thinking line control staff who acted swiftly to ensure that any risk to customers and staff was minimised."