The tornado which caused severe damage to parts of Birmingham was the most damaging in the UK since January 1998, experts said last night.
The last freak weather storm to hit the UK was at Selsey in West Sussex.
Investigators from the Tornado and Storm Research Organisation (Torro) measured a damage path which was more than seven miles (11km) long and, in places, 500 metres wide following last Thursday's twister.
The tornado was estimated at T4-5 on the T-scale of tornado intensity, with winds possibly exceeding 140mph. Another couple of tornados affected parts of Peterborough and Lincolnshire later in the afternoon, and there are also unconfirmed reports of one in Leicestershire.
The Birmingham tornado developed within a strong thunderstorm, which was moving up from the south.
The wind close to the surface was blowing from the east or north-east, but just a few hundred metres higher it was blowing strongly from the south.
The result of this is that the air acquires horizontal vorticity - that is, it has a tendency to rotate horizontally. If a passing thunderstorm updraught starts to lift this air, the rotation is tilted into the vertical. If the updraught is strong enough, the rotation will strengthen until a tornado develops.
According to experts, last Thursday's extreme weather demonstrated that the UK can get powerful tornados, and it has done in the past.
However, there is no indication that tornados are becoming more common in the UK.