Officers were called to Brigstock Road just after 11pm on Friday.
It was reported that a car had collided with a pedestrian.
The pedestrian, a man aged in his 60s, was taken to hospital in a critical condition.
His family has been informed and will be supported by specialist officers.
The driver of the vehicle, a 37-year-old man, was arrested on suspicion of driving offences including serious injury by dangerous driving, he has been bailed to a date in mid-November.
The investigation is being led by officers from the Met’s Serious Collision Investigation Unit.
Any witnesses or anyone with any information is asked to call police on 020 8285 1574 or contact via Twitter @MetCC. Please quote CAD 8850/18Aug.
In particular, officers are keen to hear from anyone who has dash cam footage of the collision or the events leading up to it.
To give information anonymously contact Crimestoppers on 0800 555 111.