ter the deluge overwhelmed pumping stations. (Anthony Devlin / AP)

Flood levels have peaked just two inches short of the height which would have swamped a major power station - leaving 500,000 homes without electricity.

Walham serves 500,000 homesThe Environment Agency said the River Severn at Gloucester had stopped rising just below the main quay wall which protects the city centre and Walham Substation.

Walham serves homes in Gloucestershire and South Wales.

Officials had been battling to keep power running at the substation by erecting barriers and pumping the water out.

Britain is suffering its worst flooding in living memory, leaving tens of thousands of people without power or water.

There have been mass evacuations across central and southern England with thousands of homes flooded.

Two of Britain's major rivers - the Avon and the Severn - have already burst their banks.

The Thames is in danger of bursting soon, threatening areas in the Home Counties and London.

Experts are considering closing the Thames Barrier at Greenwich in the morning, to help lower water levels and prevent flooding in the London area.

Waters have peaked on the Thames at Abingdon and Henley, with the highest levels at Oxford expected in the early hours of the morning.

Floods are expected to peak on the River Great Ouse at Bedford tomorrow morning and on the Thames at Reading in the early hours of Wednesday, and Windsor on Thursday.

But with unsettled weather forecast over the next three to four days, flood experts said it would not take much for river levels to start rising again.

Environment Secretary Hilary Benn has told MPs the flooding emergency is "far from over".

Sunset over flooded Gloucestershire pic: Andy CoatesThe Environment Agency has issued flood warnings for several stretches of the Thames from Oxford, through Windsor to Shepperton and Teddington.

Police in Gloucestershire have warned that the "unprecedented" crisis has not passed.

Worst flooding for decadesMonsoon-like rainstorms have overwhelmed swathes of Oxfordshire, Worcestershire, Warwickshire and Gloucestershire - and insurers have said the final repair bill could top £2bn.

The floods have been described as the worst in modern history.

An Environment Agency spokesman said: "We have not seen flooding of this magnitude before. The benchmark was 1947 and this has already exceeded it."

Stranded residents have been evacuated from their houses by helicopter, and massive disruption has been caused to road and rail networks.

Gordon Brown has been to Gloucestershire to see the devastation caused by flooding.

The crisis has sparked panic-buying in supermarkets, with shortages of milk, bread, water and petrol.

Forecasters have said there will be no let-up in the rainfall in the week ahead.