Dramatic video footage shows the scaffolding strewn across the road after it collapsed in Pond Street, Hampstead Heath.
London Fire Brigade said buildings were evacuated as a precaution but nobody was injured in the incident.
One witness reportedly said there was “an awful lot of screaming” when the structure collapsed in 55mph winds that hit London on Thursday.
Hilary Barnes told the Camden New Journal: “As we were waiting there this whole thing, it goes up the whole of the building, it started to very slowly go outward and then it buckled. It was extraordinary.
“There was an awful lot of screaming. Ambulances were charging down there within seconds. It looked like the wind called the polythene and the scaffolding came away.”
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A London Ambulance Service spokesman said they were called at 2.45pm and sent ambulance crews as well as London’s Air Ambulance and members of our Hazardous Area Response Team.
“We are working closely with other members of the emergency services and remain at the scene.”