A Bromley man was threatened with a knife at Grove Park station last week on a train travelling from Charing Cross to Orpington.
Police were called to a report a 44-year-old man from Bromley had been threatened with a knife on Wednesday, August 13.
A British Transport Police spokesman said: "A full search of the area was carried out, but nobody was found.
"Enquiries are ongoing."
Anyone who witnessed the incident or has any other information should contact Andrew Parkes on 01689 885706.
- Six south-east London stations to have NO London Bridge trains until 2018
- UPDATED TRAFFIC WARNING: Drivers STILL queuing on approach to Dartford Crossing 10 hours after crash
- Woman suffers head injury after being hit by car in Orpington
- TfL seek damages after Blackwall Tunnel diesel spill
- Eight men charged with drug offences after raids in Thamesmead