Police have said that a pensioner found collapsed in a Thornton Heath street may have been hit by a slow moving car.
Officers are appealing for help locating the driver of a grey people carrier who is believed to have been in the area at the time of the incident.
The 68-year-old man was found lying on the ground in London Road on Wednesday (March 7) at about 2pm.
The London Ambulance Service (LAS) treated the man at the scene and he was taken to a south London hospital in a critical condition.
He remains in hospital, where police have described his condition as life-threatening.
Detective Constable Sue Chalmers, from the Met’s Roads and Transport Policing Command, said: “The man has sadly suffered serious injuries as a result of this incident and I am keen to get to the bottom of exactly what happened.
“I believe the driver of the grey car stopped at the scene and helped direct traffic but left before the ambulance service arrived.
“I would like to speak to him as he may have more information about what happened in the lead up to the incident.”
Anyone with information is asked to call police on 101 quoting reference CAD 4311/16 March. To remain anonymous call Crimestoppers on 0800 555 111.