A motorcyclist has died after a crash involving a Mini Cooper on the M4.
Police were called to the eastbound carriageway, between junction 4 and 4a, to reports of a collision on Wednesday at 7.30pm.
Emergency services including London's Air Ambulance arrived at the incident, near Heathrow Airport, and found a 29-year-old man with serious injuries.
Paramedics battled to save him but he was pronounced dead at the scene.
Police are now appealing for drivers with dashcam footage to come forward.
A Met Police spokesman said: "Anyone who witnessed the collision or the events leading up to the collision, or any driver with dashcam footage, is asked to contact the Serious Collision Investigation Unit.
He added: "The driver of the car stopped at the scene - there has been no arrest."
Call Serious Collision Investigation Unit on 02082469820 or call 101 and quote CAD7173/17June.