An 18-year-old cyclist was rushed to hospital following a collision with a lorry.
The incident, which took place this morning, led to severe traffic delays along the A3, Clapham Common South Side.
A spokeswoman for the London Ambulance Service said: "We were called at 11.30am to reports of a road traffic collision involving a cyclist and a lorry in Clapham High Street.
"We sent two single responders in cars and an ambulance crew. Staff treated an 18-year-old man. He was taken as a priority to King's College Hospital with leg injuries."
The spokeswoman said the teenager was "conscious and breathing" when treated by paramedics.