British Transport Police (BTP) detectives are appealing for information after a teenage girl was followed and touched inappropriately on a train in Essex.

Investigators have released a CCTV image of a man they would like to speak to in connection with the incident, which took place on Wednesday, 14 March.

Detective Constable Alan Reed, investigating officer, said: “The victim, an 18-year-old from Ongar, boarded a train at Brentwood around 8.50am. Throughout the journey she noticed a man, who was already on the train when she boarded, staring at her, which made her feel extremely uncomfortable.

“They both left the service at Shenfield to board another train heading towards Chelmsford. Whilst on the second train, she felt him touch her inappropriately on the leg.”

Police have conducted several lines of enquiry, including anniversary visits along the route and speaking to regular commuters. After viewing CCTV in the area and from the train, officers have isolated an image of a man they believe may have key information about the incident.

DC Reed added: “This must have been a very frightening experience for the victim, who felt she was being followed.

“Incidents like this are very rare on the rail network but we treat them very seriously. I’d ask anyone who recognises the man pictured, or if indeed you are him, to come forward and assist us in this investigation.”

Anyone with information is asked to contact British Transport Police on 0800 40 50 40 quoting B5/LNA of 03/05/2012. Information can also be passed to the independent charity Crimestoppers, anonymously, on 0800 555 111.