Southwark Police have appealed for witnesses to come forward after a man was injured in an "unprovoked attack" outside Tate Modern at Bankside.
Police were called to Bankside at about 6.25pm on Tuesday 11 February.
When they arrived, officers attended to a 42-year-old man who had been punched in the face.
The man received hospital treatment for injuries to his cheekbone and jaw.
The suspect is described as a white male, aged between 30 and 35 years.
He is believed to be around 5ft 8ins tall and was wearing dark trousers, a dark hoody, dark beanie hat and a dark rucksack.
Police say that the suspect was seen by other members of the public behaving in a disorderly manner "potentially due to drink".
Cathedrals ward Sergeant Dave Hunt said: "This was an unprovoked attack and we appeal to anyone who may have been in the area to make contact with us."
Anyone with information is asked to call 020 7232 6244.