Detectives are appealing for witnesses following a collision in Ilford.
Police were called at 06:53hrs on Tuesday, 23 May to a collision between a motorcycle and car on the A12 near the junction with Quebec Road.
The 26-year-old motorcyclist was taken to hospital where he remains in a critical but stable condition.
The driver of the car stopped at the scene. No arrests have been made.
Anyone who witnessed the collision is asked to call investigating officers from the Roads and Transport Policing Command based at Chadwell Heath on 020 8345 4847.