Detectives are appealing for witnesses and dash cam footage of an incident involving a silver coloured BMW in Greenford.
Police were called at 01:05hrs on Wednesday, 21 November to reports of a silver BMW in collision with a parked vehicle at Whitton Road East, junction with Ridding Lane.
Officers, London Ambulance Service and London Fire Brigade attended the scene.
Three males in the left hand drive, silver coloured BMW were taken to a north London hospital where one 24-year-old male remains in a critical condition.
Detectives from the Roads and Transport Policing Command investigate.
Officers are keen to speak with anyone who was in and around the area at the time of the collision, or any motorists who may have captured any part of the incident or the BMW being driven prior to the collision on dash cam.
There have been no arrests at this time. Enquiries continue.
Any witnesses or anyone with information should contact the witness appeal line at Alperton Traffic Garage on 020 8991 9555 or via 101 quoting reference 2528310/18.
Information can also be reported anonymously to Crimestoppers on 0800 555 111 or online at crimestoppers-uk.org.