The 'biblical' deluge that broke all the records

Emergency services were today readying themselves for more heavy rain after England's wettest day on record claimed the life of a "heroic" policeman and left thousands of others counting the cost of flooded homes and businesses.

The extreme rainfall that swamped northern England with devastating floods, sweeping away bridges, making hundreds homeless and killing a policeman, was the heaviest ever recorded in Britain in a 24-hour period.

More than a foot of rain – 12.3in – fell on to the Lake District in 24 hours, breaking the previous record set in a summer thunderstorm in July 1955, when 11in were recorded in Martinstown, Dorset, the Environment Agency said.

The new record – 314.4mm – was recorded at the Environment Agency gauge at the hamlet of Seathwaite in Borrowdale, near the head of the River Derwent. The unparalleled volume of water, running off already saturated ground, turned the Derwent into an unstoppable torrent which devastated the towns in its path, Cockermouth and Workington – collapsing a stone bridge on Workington's outskirts and killing PC Bill Barker, who was guiding people away from it.

The downpour was caused by a wet, warm air system blown across the Atlantic, which sat over Cumbria for 24 hours and brought the equivalent of nearly two months' rain in a single day. Although its intensity cannot on its own be ascribed to climate change, it is consistent with predictions of what a warmer world will mean for Britain.

The unprecedented nature of the rainfall was emphasised yesterday by the Environment Secretary, Hilary Benn, who said it was probably a "one-in-a-1,000-years event". And there were warnings that more rain, albeit not of the same severity, was expected in today.

West Cumbria, particularly Cockermouth, bore the brunt of the devastation. Four bridges collapsed, main roads were blocked, 39 schools were closed and more than 200 people were forced to leave their homes.

Water levels rose to almost 8ft on the worst-affected streets, and fire crews had to pump water out of homes. The weather was so severe that lifeboats deployed to rescue people had to turn back. More than 1,200 people were left without electricity.

In Workington, PC Bill Barker fell victim to the ferocity of the weather. The 44-year-old was attempting to protect people trying to cross Northside bridge when the swollen river washed the structure away. His body was found yesterday afternoon washed up on a beach at Allonby, 10 miles north of Workington.

PC Barker, a family liaison officer who had served with Cumbria Police for 25 years, would have been 45 today. He leaves a wife and four children. His wife, Hazel, said: "How do you put into words how you feel about somebody you are so proud of?

"Bill was my best friend, my forever friend, and an amazing dad. I have the comfort of knowing that Bill died doing the job he loved, and the fact that he was helping others is typical Bill."

The Prime Minister, the Home Secretary Alan Johnson and the Conservative leader David Cameron also paid tribute to PC Barker. The Chief Constable of Cumbria Police Craig Mackey said: "Bill is a hero who died saving the lives of others and our thoughts are with his family at this devastating time. He was a much-loved friend, colleague and an inspiration to everyone he knew."

The floods were even worse than those that engulfed Cumbria in 2005.

Gordon Brown said that he had assured Mr Mackey that any help he needed would be provided. "Our thoughts are with all those who have been impacted by these floods and our thanks go out to the emergency services who continue their extraordinary efforts to help the people affected," he said.

The Prime Minister said that he had been in contact with the Environment Secretary Hilary Benn who was in Cumbria to assess the situation. Mr Benn, in Cockermouth, said that even defences built after the floods of 2005 to withstand a "one-in-100-years flood" could not cope. "What we dealt with was probably more like one-in-1,000, so even the very best defences, if you have such quantities of rain in such a short space of time, can be over-topped," he said.

He warned that, while the flood waters were beginning to go down, more rain was forecast. "It is very important that people listen out for warnings, follow the advice that they are given, and look out for elderly neighbours or relatives," he added. Last night 34 flood warnings, four of them severe, were in place in Cumbria. A further 11 were in place in the North-east and the Midlands.

Workington's MP Tony Cunningham said the flood was "of biblical proportions" and added: "The scale and the force of the devastation in Cockermouth is huge." Pete Marston, who lives in Cockermouth, added: "It's going to take the town years to recover from this."