British Transport Police officers are appealing for the victim of an alleged sexual assault to come forward.
The incident happened on Thursday, 19 February, at around 7.35pm in coach D on the Chester to Euston service.
The victim was verbally abused and indecently assaulted before leaving the train at Crewe.
Members of public were alerted by the man’s obscene language and reported him to the train manager.
A 39- year-old man from London was met by officers at Euston station and arrested.
Investigating officer PC Mark Parfitt said:
“I am really keen to trace the woman who was allegedly assaulted. If you were travelling on this train and witnessed this incident, please get in touch with BTP. Any information could prove vital to this investigation.”
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference PSUB/B7 of 20/02/15.
Information can also be passed anonymously to independent charity Crimestoppers on 0800 555 111.