The incident happened at Gallions Reach Health Centre in Bentham Road at 8.06pm yesterday (November 16).
Paramedics had responded to reports of a crash involving a car and pedestrian.
At the scene, a 17-year-old boy was found injured and taken to hospital.
His condition remains critical.
Officers arrested a 16-year-old boy on suspicion of causing injury by dangerous driving, driving without a licence, and theft of a motor vehicle.
A spokesperson for the Met said: “Police were called by the London Ambulance Service at 20:06hrs on Sunday, 16 November after reports of a collision between a car and a pedestrian on Bentham Road, Thamesmead.
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“A 17-year-old boy was taken to hospital where he remains in a life-threatening condition.
“A 16-year-old boy has been arrested on suspicion of causing injury by dangerous driving, driving without insurance, driving without a license and theft of a motor vehicle. He remains in custody.”
If you saw anything or have information that could help police, please call 101 quoting CAD 6506/16Nov.
