The incident happened in Rushey Green near Lewisham High Street at around 7am yesterday (October 18).
Officers and London Ambulance Service crews attended and found a man injured.
He was taken to hospital for treatment where his condition was initially unknown.
A spokesperson for the Metropolitan Police confirmed today (October 19) that he is in a life-changing condition.
No arrests have been made as police enquiries continue.
The full statement from Metropolitan Police says: “At around 07:00hrs on Saturday, 18 October, police responded to a report of a road traffic collision between a van and a pedestrian in Lewisham High Street, SE13.
“Officers attended the scene alongside the London Ambulance Service, London Fire Brigade and London’s Air Ambulance.
“A 54-year-old man was taken to hospital for treatment. We await an update on his condition.
“There have been no arrests and enquires are ongoing.
“Please call police on 101 with the reference 1600/18OCT if you were a witness or have any footage including dashcam.”
