Only the actions of a quick-thinking driver of a packed rush-hour train from Margate to Cannon Street ensured that no accident occurred.
He was forced to hit the brakes when he realised he was on a collision course with another train bound for west London which was just leaving on the same track a few minutes before 9am.
A crash was averted but in the process one coach on the outbound train - leaving for Hayes - came off the track. Both trains involved were operating on Connex South Eastern routes.
Railtrack - which owns stations and track - insisted both trains were travelling "very slowly - at the most 15mph". "Our information is that there were no injuries," said a spokeswoman for the company. There were no reports of casualties.
An investigation was launched immediately by the safety authorities, the train company and Railtrack.
Early reports suggested that one train had "jumped a signal" were denied by Railtrack.
"It will one of the things that will be looked at by the investigators," said a spokesman for Railtrack.
The incident caused long delays with services being severely disrupted right into the evening rush-hour as engineers worked to get the derailed train back on track.
For most of the day, services ran out of London Bridge station rather than Cannon Street - with special shuttle trains running between the two termini.
Yesterday's near-miss brought back memories of a serious accident at the station in January 1991, when a packed commuter train smashed into the buffers. Two people were killed and hundreds injured.
t The Health and Safety Executive yesterday published its official report into the crash in August 1996 at Watford, Hertfordshire, in which a woman passenger was killed.
The report concluded that the the primary cause of the crash was a driver going through a red signal, and the executive urged Railtrack to examine thoroughly the question of trains passing stop signals.Reuse content