Six hurt as tornado hits London
Rooftops were ripped off and cars were badly damaged as the twister hit the Kensal Rise area of north-west London.
One man suffered a serious head injury and five have been treated for minor injuries and shock.
Fire services have sealed six roads in a zone covering a quarter of a square mile and searched 100 properties.
Fire crews were called at about 1100 GMT on Thursday to Chamberlayne Road and surrounding streets, amid reports of collapsed scaffolding and damage to buildings.
Witnesses said there was heavy rain and sleet, then debris flying through the air.
Resident Colin Brewer said: "It was really, really incredible. All of a sudden I saw a swirl starting to form and then, it was amazing, but it then touched land.
"I then saw clumps of all sorts of things flying into air.
"It went from exciting to terrifying."
He reported seeing trees ripped up from the roots, front doors missing, windows smashed and people being hit on the head by flying objects.
The UK experiences an estimated 50 tornadoes on land each year, putting it top of the European twister league.
The BBC Weather Centre said the tornado lasted less than minute.
"To see a tornado is not that unusual - but the magnitude of the damage due to the one in north-west London is," said BBC meteorologist Susan Powell.
She said the tornado formed due to a lot of energy in the air across the UK, producing widespread heavy thunderstorms with gusty winds.
"However, in the case of the shower in London, the massive up and down draughts came into phase, spiralling and forming a tornado," she said.
Local resident Daniel Bidgood : "I was in my living room and I heard a big crack of lightning and thunder, then as I went to the window I heard a sound which was like standing behind a jetliner.
"I could see a huge cloud rolling up the street, making this tremendous sound.
"I went to try to take a picture of it but a shower of debris smashed all the windows of my house."
London Ambulance Service said a man, thought to be in his 50s, was treated for a head injury and is expected to be released from hospital later on Thursday. Five others were treated for shock and minor injuries at the scene.
Dave Bonner, of the London Fire Brigade, said about 50 fire fighters have searched over 100 properties and found several people injured.
Residents will not be allowed to return to their homes until the area is deemed safe.
Brent Council has set up a respite centre at the nearby Church of the Transfiguration for residents who have been made temporarily homeless.
"The council has sent officers, including tree and building experts, and contractors, to help with removing fallen trees and damaged properties," said a council statement.
Insurance experts said it was too early to estimate the cost of the damage, but the 2005 Birmingham tornado ran into tens of millions of pounds.