A woman suffered alleged racist abuse on a train which set off from Doncaster.
British Transport Police officers said a man was in the quiet carriage of a Virgin Trains East Coast service being loud.
The victim – a woman in her twenties – asked him to be quiet but was verbally abused in response and the language was racially motivated.
The incident happened on a train between Doncaster and Newark Northgate stations between 6pm to 630pm on Saturday, February 3.
Officers would like to speak to the man pictured in the CCTV image. They believe he could help them in their investigation.
Any information on the man's identity can be passed to BTP by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 536 of February 3, 2018.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.