On Wednesday (February 19) police were notified that a man in his 60s was in hospital in a critical condition.
The man died from his injuries in hospital a day after the report was made (February 20).
A post-mortem examination is set to take place at a later date.
Following enquiries made by the force, the man was believed to have been assaulted early on Sunday morning (February 16) outside a property on Malton Street in Plumstead.
A 44-year-old man was arrested on suspicion of grievous bodily harm and has been released on bail whilst enquiries continue.
A spokesperson for Metropolitan Police said: “Officers are continuing to investigate a serious assault in Plumstead.
“On Wednesday 19 February, police received a report that a man was in hospital in a critical condition. Enquiries indicated that the man had been assaulted on the morning of Sunday, 16 February outside an address on Malton Street, Plumstead.
“Officers arrested a 44-year-old man on suspicion of grievous bodily harm. He has since been released on bail whilst enquiries continue.
“Sadly, the victim, who was in his 60s, died in hospital on Thursday, 20 February. A post mortem is yet to take place. Enquiries remain ongoing.”
