A pedestrian has died after being struck by two cars near Buckingham Palace.
The unidentified woman was pronounced dead shortly after the collision at 2.20am at The Mall in central London, Scotland Yard said.
The driver of the second car, a blue Mercedes e-Class, drove off from the incident.
But police later traced the vehicle to an address in Hendon, north London, and arrested a man on suspicion of causing death by careless driving and failing to stop.
The driver of a black Mercedes e-Class, which hit the woman first, stopped at the scene.
A police spokesman said inquiries are under way to identify the woman, who is described as of heavy build with collar length dark brown hair.
Officers from the Road Death Investigation Unit are investigating.