A male cyclist has been taken to hospital with life-threatening head injuries after his bike was in a collision with a car.
Police say the accident happened at around 10.20am on Charlie Brown's roundabout in South Woodford, near the junction with Chigwell Road.
The driver stopped at the scene and no arrests have been made.
There is currently slow traffic in the area, with the A406 eastbound remaining closed.
The Guardian is awaiting further information.