Detectives are appealing for witnesses and those with dash cam footage to make contact after a fail-to-stop collision in Croydon.
Police were called at 21:54hrs on Saturday, 2 January to A232 Wickham Road, at the crossroads with Hartland Way and Orchard Avenue.
A moped or motorcycle was involved in a collision with a 66-year-old female pedestrian.
She was taken to hospital, where she remains in a critical condition.
The rider did not stop at the scene.
Detectives from the Met's Serious Collision Investigation Unit are urging anyone who saw the incident or may have captured it or the events leading up to it on dash cam video to make contact via 0208 285 1574.
Alternatively call 101 ref CAD 6309/2 Jan, or tweet @MetCC.
To remain 100% anonymous contact the independent charity Crimestoppers on 0800 555 111 or crimestoppers-uk.org.