A man suffered a serious head injury when he was assaulted in Spa Gardens, Grange Road, Bermondsey on Sunday afternoon.
Police were called at approximately 2.10pm on Sunday to reports of a man having been seriously assaulted in Bermondsey Spa Gardens.
Officers discovered a 39-year-old man lying unconscious on the ground suffering from a serious head injury.
The man was taken by ambulance to a London hospital where he remains unconscious. His condition is described as "serious".
Police believe that two male suspects engaged in conversation with the victim before they assaulted him. Both men then made off on foot towards Grange Road.
The suspects are described as white, aged approx 25 years. One is described as taller than the other and both wore baseball type caps and T-shirts.
"This was a senseless, unprovoked attack on a man who was unable to defend himself," says DI Dave Willis.
"We would urge anyone who has any information to come forward as a matter of urgency and help us catch those responsible".
Anyone who witnessed the incident or anyone with information is asked to contact Southwark CID on 020 7232 6166. If you wish to remain anonymous contact Crimestoppers on 0800 555 111.
No arrests have been made and the police inquiry continues.