Police were called to Charlotte Despard Avenue, SW11 at 16.32hrs on Saturday, 25 May.
Officers attended and found a 46-year-old man suffering a head injury. London Ambulance Service attended and the man was taken to the hospital. Sadly, he died at the hospital on Tuesday, 28 May.
A post-mortem examination will be held in due course. Officers believe they know the identity of the deceased, but await formal identification and confirmation that all next of kin have been informed.
It is believed that, shortly before the victim was assaulted, he had approached a group of males who were attempting to steal his moped which was parked nearby, in a car park near to shops off Battersea Park Road.
The victim was attacked in the street by this group of males, who made off prior to the arrival of police.
The moped was not stolen. It has been recovered by police and is subject to forensic examination.
A 16-year-old male was arrested near to the scene a short time later on suspicion of GBH. He was taken to a west London police station and has been bailed to a date in early June pending further enquiries.
The police investigation – now a murder inquiry – is being led by detectives from the Homicide and Major Crime Command.