A man exposed himself to two schoolgirls on a Brighton to London train.
Detectives from the British Transport Police (BTP) have asked for help tracing the man who officers believe may have been a holidaymaker.
Detective Constable Sarah Garden, the investigating officer, said: “The two girls, who were part of a group, were travelling back from a school visit when the incident happened.
“A short while into their journey, they noticed that the man next to them was exposing himself beneath a newspaper and was also performing an indecent act.
“After the girls left the train at London’s Victoria station the man entered the train toilet.”
Police have carried out a number of inquiries to try to establish the identity of the man, including speaking to witnesses and circulating images on police intelligence systems, but to no avail.
DC Garden said: “We have now isolated an image and are looking for anyone who may recognise the man pictured to come forward.
“He may well have been holidaying in the area, so we are also asking any B&B owners who may know the man to contact us.
“The man’s actions were completely unacceptable and understandably the incident left the victims upset and distressed.
“If you have any information about the incident, however small, we would really like to speak to you.”
The incident happened on Thursday 5 July between 5.30pm and 6pm on the 5.19pm train which arrived at Victoria at 6.14pm.
Anyone with information about the man or the incident is asked to contact the BTP on Freefone 0800 405040 or the independent charity Crimestoppers anonymously on 0800 555111.