A gay man was stabbed in Northlands Street, Camberwell on Saturday 2nd August.
Police and an ambulance attended the scene and Andrew Pratt, 43, was taken to Kings College Hospital.
Mr. Pratt died of a single stab wound to the heart just before midnight.
Mr. Pratt, a manager at the Emilio Pucci fashion store, lived with his ex-partner in Brixton and is to believed to have been fighting off a robbery suspect.
The suspect is described as a black man in his thirties with dreadlocks and short facial hair, approximately 6ft tall and of proportionate, strong build, and was wearing a grey hooded top.
The incident took place at around 10.35pm.
Police do not think the incident was motivated by homophobia.
Anyone with information is asked to call the incident room at Lewisham on 020 8721 4906.
If you wish to remain anonymous call Crimestoppers on 0800 555 111.