At just after 6pm on Sunday 6 February, a woman was travelling on the service when a group of football fans boarded at Crewe station having attended a fixture in Liverpool.
A man holding a bottle of wine then approached the woman and sat next to her before repeatedly asking for her name.
He then told her he wanted to kiss her and touched her inappropriately. She told him to get off and he replied, “there is nowhere for you to go”.
She then moved down the carriage to get away from the man and stood with two Cardiff football fans and a woman who witnessed the incident.
The man is described as white, in his mid-50s, of medium build, with brown hair cut short. On the day he was wearing a black gilet, navy jumper and blue jeans.
Officers would like anyone who witnessed the incident to come forward to assist them with their enquiries.
They are particularly keen to speak to the two Cardiff City FC fans and the woman who stood with the victim on the train after the incident.
Witnesses, or anyone with information, can contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 2200011710.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.