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.
- Blackheath and Woolwich gynaecologist struck off after squeezing patient's nipples to see if they were 'still milking'
- UKIP chooses candidates for Dartford Council by-elections
- Man, 22, arrested over Thamesmead murder of Ben Fasina
- Panic at Lewisham Hospital after someone shouts 'Ebola' following admission of patient by staff wearing biohazard suits
- Pro golfer-turned police officer back on the golf course to take a swing at anti-social youths