A 19-year-old man has been arrested after a teenage girl was raped in a train cubicle.
The victim, a 17-year-old girl, was in the train toilet at just after 2.30pm when she was sexually assaulted by another passenger.
A man has been released on police bail while enquiries continue.
Officers are asking anyone with information to come forward.
A spokesperson for British Transport Police said: “Officers investigating a rape on-board a service travelling between Eltham and Dartford are appealing for witnesses or anyone with information.
“At just after 2.30pm on Friday 20 May, a 17-year-old girl was raped in one of the train’s toilet cubicles.
“A 19-year-old man has been arrested in connection and released on police bail pending further enquiries.
“Officers are keen to speak to any witnesses or anyone with information to assist their investigation.”