Police are appealing for information after a man was left in a critical condition when he was assaulted in Elephant & Castle.
The 46-year-old man was drinking in the Distriandina bar in Elephant Road at about 4am on Sunday morning.
He had an argument with the suspect before he was assaulted by the man.
He was taken to a south London hospital with head injuries. He is currently in a critical condition.
The suspect is described as a man in his twenties wearing a dark long-sleeved top and dark jeans.
He was seen walking away in the company of a woman towards the junction of Elephant Road and Walworth Road.
"Police inquiries are ongoing into this attack," said Detective Inspector Teresa Foster.
"The attack has left a man in a critical condition and I would urge anyone with information or who knows the suspect to contact us."
Anyone with information is asked to call Southwark CID on 020 7232 6218. If you wish to remain anonymous call Crimestoppers on 0800 555 111.