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.
- Crowd trouble at Rotherham v Millwall game
- Fawkham nudists battle to save caravans at naturist club
- VIDEO: Has a ghost been caught on film at Orpington Priory?
- New Cross teen charged with firearms offences
- VIDEO: Funny or plain stupid? Gravesend prankster, Daniel Jarvis, attempts to give police officers parking fines