At 12.30am on Sunday 16 October, the victim boarded the train at Liverpool Street station and sat with a group of passengers.
Shortly after, an altercation broke out between the victim and a man sat in the aisle seat next to him.
The man repeatedly punched him and kneed him in the head, causing him to fall unconscious.
The man then alighted the train at Romford station and left the scene.
If you recognise him, or have any information, please contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 33 of 16/10/22.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.
