Man in dress exposed himself on Lincoln-Grimsby train
CCTV has been released after a man wearing a dress and no underwear exposed himself on a train travelling between Lincoln and Grimsby.
A female passenger complained a group of men boarded the train and began shouting and swearing, police said.
One of them, wearing the dress, climbed on to a seat and exposed himself to the woman and others in the carriage.
It happened at about 19:30 BST on the 18:35 service from Lincoln on 14 July but the images have just been released.
PC Rachael Croft said: "The man's actions were completely unacceptable.
"What he may have perceived as fun was in fact very upsetting and distressing for the other passengers on the train."
The men left the train at Grimsby but they were not traced, despite a search by officers shortly afterwards.
British Transport Police want to speak to the man pictured in connection with the incident.
They also want to speak to people who witnessed what happened.