At 1pm on Monday 7 February, a woman boarded the service and a man looked at her and said, “hey baby”. She ignored him and moved to another part of the train.
Later in the journey, she noticed the man had moved closer to her before he exposed himself inappropriately and started masturbating.
Officers believe the man in the image may have information that could help their investigation.
If you recognise him, or have any information, please contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 338 of 07/02/22.
Alternatively, call Crimestoppers anonymously on 0800 555 111.