Three people died and several others were missing last night after torrential rain caused flooding across much of Britain.

The man who died got stuck after he slipped while trying to clear a drain in Hull. Firefighters and divers spent several hours trying to rescue the victim - believed to be in his 20s - after his foot became trapped in a metal grate. He died despite rescuers' efforts.

In Scotland, which escaped the worst of the floods, fears were growing last night for the safety of a lorry driver who is thought to have gone into a swollen river.

A helicopter and two rescue teams spent several hours yesterday scouring the area of the Leaderfoot Viaduct near Melrose in the Borders looking for 51-year-old Philip Shoemaker.

His car was found beside the River Tweed shortly after 7am and police said that due to the flooding, it was believed he may have entered the water.

But one of the worst affected areas last night was South Yorkshire, where several rescue operations were under way. In Sheffield, police were investigating reports that a teenager had fallen into the River Sheaf at Millhouses Park in the city. A helicopter from South Yorkshire Police was being used to search for the boy, who was reported to have been swept away at about 5.15pm.

Severe weather warnings were issued throughout the day and hundreds of homes were evacuated. Also in the city, around 20 people were being airlifted from the roof of a building after they became trapped by the rising waters.

Other buildings in the area were also surrounded with water. Greg Wood, who was stranded with around 200 colleagues in the first-floor canteen of Sheffield's Royal Mail distribution centre, said: "We just can't get out because of the amount of water.

"There's several feet of water. It's contaminated with sewage and everything. We can't wade through it because it's not safe.

"We're going to stay here until we're told to do otherwise.

"We've got no power, we can't watch the TV, we can only see what's out the windows. We had to turn the generators off because the power is under water level."

Humberside Fire and Rescue Service said the man who died in Hull had become trapped in a drain while trying to clear the flood water.

As the emergency crews struggled to free him, he lost consciousness and died moments later.

Glenn Ramsden, of the rescue service, said: "Despite the efforts of all the rescue team, including police divers and ourselves, we couldn't do anything to save the man.

"It's been an absolutely desperate operation to save this man but at the end of the day we couldn't do it."

Police said the Health and Safety Executive had been informed.

Pensioner Geoffrey Claxton, 76, said the victim, who had worked for Mr Claxton's family fish-importing business since he was 16, had gone to help him clear rubbish and other blockages from the drain cover. "I don't know if he'd slipped in or what," he said. "One neighbour actually dived down three times to try and free it. The force of the water was too much. He was a lovely lad and great employee. It's a total tragedy."

The dead man was named locally but Humberside Police could not confirm whether his next of kin had been informed.

Meanwhile, three men were rescued from chilly water after their speedboat sank in Loch Sween, near Lochgilphead, Argyll. The men, two of whom had no lifejackets, were thrown into the water and struggled to stay afloat until help arrived. Coastguards rescued the men, who were not injured but were taken to hospital for a check-up.

A spokesman for the Met Office said the worst-affected areas had already seen more than twice the monthly average rainfall for June. But he added the extreme conditions were expected to ease today.