Police are appealing for witnesses and footage after a female passenger died when the BMW she was in flipped over in west London.
The fatal collision happened in Uxbridge with the victim, 42, pronounced dead at the scene.
The 34-year-old driver of the silver BMW M5 was taken to a central London hospital.
His condition is not believed to be life-threatening.
Police and paramedics were scrambled to the scene on Hillingdon Hill at just after 9.20pm on Saturday.
A police statement said: “Enquiries to establish the cause of the collision continue, however it is believed the BMW may have collided with railings before overturning. There has been no arrest at this stage.”
Police are urging witnesses or anyone with dashcam footage that may have captured the incident to call the Serious Collision Investigation Unit (Team 3) on 020 8246 9820 quoting CAD 7283/13nov.