The victim, who walks with a stick, was attacked from behind as he walked down a driveway next to number three, Loughborough Park, at about 11.45 am on July 9.
The suspect approached from behind before grabbing a gold chain around his victim’s neck. The necklace had three gold trinkets dangling from it; a pair of boxing gloves, a ring and horse.
The robber, described as a black man aged 20-25 years with a shaven head, ran away along Loughborough Park to Coldharbour Lane and into Shakespeare Road. He was wearing a light grey jumper and grey bottoms.
The victim did not require medical attention.
Lambeth police are appealing for witnesses, or anyone who may have been offered the distinctive stolen jewellery.
Anyone with information should contact training detective constable Anne Hogarth on 020 8649 2440, or Crimestoppers anonymously on 0800 555111.