Police are appealing for witnesses after a cash-in-transit van was robbed in Norbury on Saturday.
Officers were called at 12.50pm to reports of a robbery of a security van, outside the Tesco Express petrol station in London Road.
The guard was approached by a young male who stole the cash box, he was assaulted but not hurt in the process.
Police say there were no reports of any firearms being used or seen.
An unspecified quantity of cash was stolen and the suspects had fled prior to police arrival.
The suspect fled the scene with a second male in a silver coloured vehicle, heading in the direction of Galpins Road.
Both men are described as black males in their late teens.
Flying squad detectives are investigating the incident.
Any witnesses or anyone with information should call the Flying Squad on 0207 232 6530 or Crimestoppers anonymously on 0800 555 111.