Detectives from the Roads and Transport Policing Command are appealing for witnesses following a collision in New Malden.
Police were called by the London Ambulance Service at 16:55hrs on Wednesday, 23 December to reports of a car in collision with a pedestrian on Clarence Avenue at the junction with High Drive.
The pedestrian, a woman aged in her late 80s, was taken to a south London hospital where she remains in a serious but stable condition.
The driver stopped at the scene.
Local roads closures have since been lifted.
Anyone with information is urged to call officers from the Serious Collision Investigation Unit at Merton on 020 8543 5157 or via 101.
Enquiries continue. There have been no arrests.