Police are investigating after a woman was sexually assaulted on board a train after she fell asleep.
British Transport Police (BTP) detectives are asking for help from the public and have released images of a man they think can help them with their investigation.
Detective Constable Andy Parkinson, leading the investigation, said: "The 25-year-old victim had been out for the evening in London with friends on Monday, 28 April. She boarded the train at Charing Cross and sat in one of the last two carriages but quickly fell asleep.
"She woke up, sometime between 12.25am and 12.50am, to find a man sexually assaulting her. The victim managed to push the man away and fled the train when it arrived at West Wickham station a few moments later."
The incident occurred on the 12.13am London Charing Cross to Hayes service on Tuesday 29 April.
Officers have been pursuing several lines of enquiry including analysing CCTV from the train and at several railway stations. They have now released CCTV images of a man they think might have crucial information.
DC Parkinson added: "We believe the man pictured boarded the train at Lewisham station and got off at West Wickham. I am eager to speak to him as I think he might have vital information. If you recognise him or think you may have witnessed the incident, please get in touch. We take all reports of sexual assault extremely seriously and are doing all we can to catch the individual responsible."
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