A man made homophobic and racist remarks towards a young woman on the service just after midnight on the 26th of February.
A man who was also travelling on the train stepped in to help but a fight broke out.
The man then disembarked at Osterley Underground station.
Officers would like to speak to the man pictured, as they believe he may have information that can help their investigation.
Anyone who recognises him or witnessed the incident is asked to contact BTP by texting 61016 or by calling 0800 40 50 40, quoting reference number 10 of 26 February.
Information can also be given anonymously to Crimestoppers on 0800 555 111.
