A man was rushed to hospital with a serious head injury after being left unconscious following an attack in Edinburgh city centre.
The 20-year-old required emergency hospital treatment after the incident on Meuse Lane on December 11 last year.
Police launched an appeal for information at the time but have since released CCTV images of four men they want to trace in connection with their probe into the assault.
The victim was later released from hospital after an investigation got under way.
All four men pictured in the images are thought to be white and in their mid-40’s.
The first is thought to be around 6ft with a medium build, bald and wearing a dark jacket at the time of the incident.
Another bald man, around 5ft 7in and wearing a dark jacket with a blue shirt underneath is also being sought by officers.
Images released by detectives show another man with a medium build, around 5ft 10in in height, and wearing a dark beanie hat, dark jacket and blue jeans.
The final man is said to have short, dark hair and was wearing a navy blazer.
Officers have encouraged the four men or anyone who recognises them to contact officers as soon as possible.
Detective constable Christopher Docherty of Edinburgh CID, said: “I would urge the men depicted in these images, or anyone who has information relating to them, to make contact with the police.
“Anyone with any information is asked to contact CID via 101, quoting incident number 3747 of Saturday, December 11, 2021.
“Alternatively, call the charity Crimestoppers on 0800 555 111 where information can be passed on anonymously.”