Mawney Road in Romford was closed last night from just after 10 pm until 4.40 am this morning following a collision.
London Ambulance Service alerted police to a collision involving a motorbike and a car at approximately 21:45hrs on Tuesday, 7 July on Mawney Road.
Officers attended and the motorcyclist, a man in his forties, was taken to hospital where he remains in a life-threatening condition.
Mawney Road was closed in both directions until approximately 04.40hrs.
The car stopped at the scene and there have been no arrests.