British Transport Police have released a CCTV image as part of an investigation into a sex assault on a woman on a train between Waterloo East and Blackheath.
PC Anne Baldwin said the 22-year-old victim reported the incident to police after she was assaulted on a train from Charing Cross on Monday 16 February.
PC Baldwin said: "The woman was already on the train at around 9.20pm when she was approached by a male who boarded the train at Waterloo East and sat next to her, despite the carriage being relatively empty.
"As the journey progressed the man is alleged to have sexually touched the woman several times. The woman managed to get away from the suspect and moved to another part of the train.
"The suspect got off the train at Blackheath. He was described as being black, with a shaved head, about 5 ft 11 in tall, and aged in his mid to late 20s. He was wearing a double breasted light beige jacket, light beige trousers, black shoes and was carrying a large black bag.
"We are keen to trace this man, as well as a potential witness who later assisted the victim. The second man was described as being a white male, aged in his 50s who had a large build. The man had white hair and a white beard. The only clothing the victim can remember seeing was a hi-visibility jacket. This male may have connections to the Eltham area.
"We are very keen to hear from the potential witness in this case, along with anyone who can identify the male captured in the CCTV image.
"We believe both males can assist us with our investigation."
Anyone with information is urged to contact BTP on 0800 40 50 40 quoting background log B6 of 23/03/09.