The victim of the assault, which happened at around 2.45am on New Year's Day, is still recovering from injuries.
He was stood by the Taxi rank when a man assaulted him with a single punch, inflicting facial injuries and causing him to fall to the floor.
He was taken to Gloucestershire Royal hospital for treatment.
PC Fraser Mackie, the investigating officer, said: “The victim is still recovering from his injuries and I hope releasing the CCTV of the assault will show the severity of this incident.
“I urge anyone who recognises themselves in the footage and haven’t already spoken to police to come forward and help us with our enquiries.
"Of course, I also want to trace the man responsible for this thoughtless and violent crime.
"Anyone who recognises him is urged to contact police.”
Anyone with information is asked to contact Gloucestershire Police on 101, quoting incident number 122 of Friday 1 January.
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