The full and devastating impact of England's worst recorded day of rain was still emerging last night as tributes were paid to a policeman swept away by floodwaters while trying to save others.

PC Bill Barker was helping motorists stranded on a bridge over the Derwent in the Cumbrian town of Workington when it collapsed. His body was discovered hours later on a nearby beach.

The Environment Agency said that the flooding across the region was so severe that such an event was likely to happen only once in 1,000 years. The rainfall, on to an already saturated terrain, was the highest level measured in England since records began. Meteorologists recorded 314mm (12in) of rain in 24 hours and flood warnings remained in place across the North West of England, parts of Wales, Scotland and Northern Ireland.

The bridge from which PC Barker fell to his death was one of at least four to be washed away. Cumbria County Council issued a warning to motorists and pedestrians to avoid using such crossings as they could be extremely dangerous. Hundreds of homes and businesses were evacuated, many of them ruined by floodwater and mud.

Jerry Graham, Cumbria's Assistant Chief Constable, said that PC Barker and a colleague had gone on to the bridge to help drivers who were trying to cross it. He said: "It was obvious they were going to put themselves in danger so PC Barker went to try and protect them. The bridge gave way just due to the volume of water and PC Barker went into the water."

The floods will cost millions. An Association of British Insurers spokesman said: "While it is far too early [to give] a precise figure, early estimates are that there will be between 500 and 1,000 claims, domestic and business. This will mean payouts of between £50 million and £100 million."

Emergency services continued to rescue those still trapped yesterday. They urged anyone who had gone to see the destruction for themselves to leave because their vehicles were blocking roads and hampering efforts to reach the worst-hit areas. In Cockermouth, the town worst hit by the flooding, people were winched from the waters. The two rivers that run through the town burst their banks, blocking roads and forcing the rescue of more than 200 people.

The Federation of Small Businesses opened its £500,000 Disaster Recovery Fund for its members in Scotland and the North West of England.

It appeared that the worst may be over early this morning as flood levels dropped by about 2in an hour. Police estimated that 1,100 homes across the county were affected by flooding.