British Transport Police detectives are appealing for witnesses after a member of railway staff was pushed onto the tracks at London Bridge Station on Sunday 31 January.
An arrest has been made in connection with the incident which took place at about 1.15pm on Sunday and investigators are appealing for any witnesses to come forward.
"A man was pushed onto the tracks as a train approached," says Detective Sergeant Pete Thrush.
"Fortunately due to the diligence of station staff trains had been placed on caution and the driver brought the train to a quick stop, preventing more serious consequences."
A 37-year-old man was arrested at the scene and taken into custody.
He was later detained under the Mental Health Act. He remains in hospital where his mental health is being assessed.
DS Thrush added: "Although the victim was uninjured in the incident, there could have been grave consequences had the trains not been placed on caution.
"We would like to hear from anyone who was at the station at the time and who may have seen what took place."
Anyone with any information about the incident is asked to contact BTP on 0800 40 50 40 quoting reference B6 of 01/02/2010 or call Crimestoppers anonymously on 0800 555 111.