Two people have died and 12 have been injured after a helicopter diverted because of bad weather clipped a crane at the top of a building in central London, scattering debris as it burst into flames and plunged to the ground.
The accident happened at the height of Wednesday's morning rush hour over a densely populated residential area in Wandsworth, south of the river Thames, which is crossed by major road and rail networks.
The pilot of the twin-engine AugustaWestland AW 109 helicopter, and a person on the ground were killed.
Five people were taken to hospital and a further seven were treated at the scene, police and the ambulance service said.
Ambulances and more than 60 firefighters rushed to the scene, as people were being evacuated from homes and offices. The fires were extinguished about two hours after the crash at 0800 GMT.
The debris hit cars and surrounding buildings were set alight. One person was rescued from a burning car, witnesses said.
Long traffic delays
The accident, not far from Waterloo train station and a major bus depot, caused long traffic delays on the roads and on the public transport network.
"It was something of a miracle that this was not many, many times worse," Neil Basu of London's Metropolitan Police said.
Reports said the crane operator had survived only because he was - unusually - a few minutes late for work.
"He was halfway up to his cabin, he was making his way up by ladders when the helicopter hit," reported a lorry driver.
Residents reported hearing a massive explosion before the crash, which had made streets in the area look like a war zone.
Police said the pilot, Pete Barnes, had years of flying experience and featured in major films, such as Die Another Day and Tomb Raider II.
He also worked for a hire company that counted Prince Charles; David Cameron, UK prime minister; and the Dalai Lama among its clients.
The helicopter crashed into the crane, at the top of a tall residential and office building still under construction, after Barnes requested to divert from his route and land at a nearby heliport because of low clouds, a spokesman for London Heliport said.
The accident prompted immediate calls for a review of the number of helicopter flights over urban areas.
"We will need a real inquiry into increasing numbers of helicopters flying around London, coupled with the fact that there are so many tall new buildings," Kate Hoey, the Labour Party member of parliament for the district, said.