The victim, a 26-year-old man from Warwickshire, had just left the Voodoo Lounge night club on Swinegate when he was attacked by an unknown man after wandering into a secluded court yard.
After being knocked to the ground he was kicked to the head and body. He suffered severe bruising to his face and received treatment at York District Hospital before being discharged.
The suspect made off with the victim’s grey suit jacket which he had been wearing at York races earlier in the day.
The victim did not see the attacker so there is no description available at this time. However, officers are carrying out extensive enquiries in the area and are monitoring CCTV footage to assist the investigation.
DC Mike Avison, of York CID, said: “This was a vicious incident and the sooner the suspect is arrested and brought to justice the better for all concerned.
“We are carrying out a number of lines of enquiry to achieve this, including an appeal to the many people who were on an night out in this busy part of the city late on Friday night and the early hours of Saturday.
“Although he was unable to give a description of the robber because he was attacked from behind, I am hoping people will recall seeing the victim who was dressed in a two piece grey suit.
“Crucially, I also need to hear from anyone who possibly saw a man carrying a grey jacket or knows where he or the jacket is now.”
If anyone can help the investigation please contact North Yorkshire Police as soon as possible on 0845 60 60 24 7, quoting reference number 12110113318. Information is for the attention of DC 1245 Mike Avison at York CID.
Details can also be passed on anonymously to the independent charity Crimestoppers by calling 0800 555 111.