Downpours lasting several hours hit southern and eastern Britain, with some areas receiving half a month's rainfall in six hours.

By mid-afternoon the Environment Agency had placed two rivers on flood warning and a further 19 on flood watch.

Worst hit was Oxfordshire where fire and rescue crews were called to a number of flood-related incidents in Thame, Chinnor, Wheatley and Witney.

The county council, which also had to cope with some of the worst flooding last summer, said eight roads had been closed and a row of homes in the Tiddington area may have to be evacuated.

About 500 children were sent home from Peers School in Littlemore, Oxford, after it was feared pupils would have trouble getting home.

In Berkshire more than 100 pupils sat their GCSE history exam at Emmbrook School in Wokingham, even though 1,000 of their fellow pupils were sent home as classrooms became surrounded by floodwater and sewage.

Around 5,000 sandbags were laid at the school which required ยฃ1.5 million of repairs after it was flooded last summer.

Tony Conlan, a forecaster at MeteoGroup UK, said that much of the country had been given a soaking as the band of rain moved eastwards.

"It has been a very slow process and the rain has persisted over the same areas, and that is why we have seen some flooding.

"The worst hit areas have been Oxfordshire and counties to the south but there has also been heavy rain in parts of north-east England, Lincolnshire and Yorkshire," he said.

The Environment Agency said flood warnings had been put on the River Ray and its tributaries from Shipton Lee to Islip, Oxfordshire and The Emm Brook from Wokingham to Winnersh, Berkshire.

There was also 19 flood watches on rivers in Oxfordshire, Berkshire, Hampshire, Wiltshire, Gloucestershire and the Midlands.

Further summer gloom was predicted today by WeatherAction, a long-range forecaster which claims torrential rain will strike the country at the end of June and the start of July.

Piers Corbyn, a spokesman, said the Glastonbury music festival and Wimbledon tennis championships are likely to be hit by "exceptional deluges of torrential rain".