A Tfl bus 279 driver was assaulted after parking at its terminating spot outside South Africa House in Trafalgar Square on December 2 last year.
According to police, the suspect was asleep on the upper deck when the bus went out of service.
When the driver went to the upper deck to wake the passenger up, the suspect pushed and punched him in the face.
The 55-year-old victim suffered facial injuries. So far no arrest has been made.
Police have released an image of the man they wish to trace in connection with the assault on the driver. The suspect is described as in his 30s with short black hair and beard.
Anyone who recognises the culprit or with information is asked to contact the RTPC Reactive Crime Team by calling police on 101 quoting reference 1769/02DEC18, or Crimestoppers on 0800 555 111.