A man was left with "significant facial injuries" after being punched when he asked another man for a light for his cigarette.
The assault happened in Market Square, Bromley, just before midnight on Friday, December 10 when the victim - a man in his 30s - approached another male who ignored him and became aggressive.
Metropolitan Police have said the victim was then punched once in the head before leaving the scene.
He later went to hospital where it was confirmed he had suffered serious facial injuries which will require ongoing treatment.
Detective Constable Lucas Ainscough, who is leading the investigation, said: “This was a vicious assault which has left the victim with lasting injuries.
"The incident escalated quickly but I know there would have been several people in and around Market Square at that time of the evening.
"If you saw anything that could help the investigation, please contact police.
'This was a vicious assault...'
“I would also ask anyone who recognises the man in the image we have issued to call so we can speak to him about this incident.”
No arrest have been made and inquiries into the incident are ongoing.
Anyone with information is asked to contact police on 101 or tweet @MetCC and quote CAD3073/09FEB22.
Alternatively, you can provide information anonymously to the independent charity Crimestoppers on 0800 555 111.