Officers from the Met's Serious Collision Investigation Unit are appealing for witnesses following a road traffic collision on the A406 junction with Walthamstow Avenue just prior to Chingford turn off.
Police were called to the A406 eastbound, at 20:53hrs on Friday, 13 September to reports of a road traffic collision.
At the scene a female pedestrian believed to be aged in her forties had been in a collision with a car.
The woman has been taken to the Royal London Hospital where she remains in a life threatening condition.
Enquiries are ongoing to confirm her identity and inform her next of kin.
Anyone who witnessed this incident or has footage of the collision taking place is asked to contact Serious Collision Investigation Unit at Chadwell Heath on 0208 597 4874, via 101 or tweet @MetCC.