The attack took place on a route 483 bus in Ealing Road, Wembley, at around 8.15pm on Saturday 19 July.
The victim, a 33-year-old man, was assaulted as soon as he boarded by a man who stole his wallet. He fought back and the pair ended up at the back of the bus where the suspect forced him down into a seat.
He then knocked the victim to the floor and stamped on his head before fleeing the scene. The victim sustained cuts and bruising to his head but did not require hospital treatment.
PC Nick Kortright, from the Roads and Transport Policing Command, said: “Although the injuries sustained were not serious ones, this was a sudden and violent attack that left the victim severely shaken. We need the public’s help to identify the man in the image – please contact us as soon as possible if you have any information.”
Anyone who has information should call 101 quoting reference CAD 7931/19July. There have been no arrests; enquiries continue.