Detectives are appealing for witnesses following a serious collision in Hornchurch.
Police were called at 00:37hrs on Sunday, 8 December to reports of a collision involving a Route N365 bus and an electric scooter on Hornchurch Road at the junction with Abbs Cross Lane.
Officers and the London Ambulance Service attended.
The 43-year-old rider of the scooter was taken to an east London hospital where he remains in a critical condition. His family has been informed.
Detectives from the Roads and Transport Policing Command are investigating.
They would like to speak with anyone who saw the collision, or the moments leading up to it, or who captured it on dash cam.
The driver of the bus stopped at the scene. There have been no arrests.
Anyone with information is asked to call the Serious Collision Investigation Unit on 020 8597 4874 or via 101 quoting reference Cad 271/08Dec.