Police have released CCTV footage of the moment a man was knocked unconscious in an unprovoked attack.
The 60-year-old victim can be seen walking alone through Kings Walk in Gloucester at about 4.15am on Saturday January 10.
A man suddenly approaches the victim and, without warning, leans back and punches him in the head.
CCTV footage shows the victim falling to the ground before lying motionless as his attacker runs off.
The victim was later taken to hospital where he required eight staples for a head wound and serious facial injuries.
A spokeswoman for Gloucestershire Police said: "The offender is described as white, in his 20s, wearing a blue hoodie, light trousers and trainers with a white sole. He is carrying a black coat or jacket.
"There was a second man seen running off with the offender - he has short dark hair and was wearing a grey/green shirt, dark trousers and shoes with a white sole.
"Gloucestershire Police have CCTV footage which has captured the assault in full. They would like to hear from anyone who witnessed the assault or was in the area at the time.
"They would also like to hear from anyone who recognises the offender from the CCTV footage."
Anyone with information is asked to contact the force on 101, quoting incident number 74 of January 10.