Britain may have become an island after a Biblical-style flood split it from Europe in less than 24 hours, according to new geological research.
The flood would have taken place between 400,000 and 200,000 years ago, sweeping away hills between Britain and what is now France.
The theory could rewrite British prehistory, as current text-books teach that Britain – once a peninsula of continental Europe – split from the great land mass after a long process of erosion and rises in sea levels.
However, surveys of the Channel bed using new sonar techniques have revealed the remains of a huge valley, running south-west from the Strait of Dover.
The sonar survey, led by Sanjeev Gupta, from Imperial College, London, uncovered deep bowls, scour marks and piles of rubble on the sea bed that may have been caused by a torrent of water.
Dr Gupta said in a paper published at an academic conference: “In places, this valley is more than seven miles wide and 170 ft deep, with vertical sides. Its nearest geological parallels are found not on Earth but in the monumental flood terrains of the planet Mars.
“This suggests the valley was created by a catastrophic flood following the breaching of the Dover Strait and the sudden release of water from a giant lake to the north.”
According to Dr Gupta’s theory, France and Britain would have been linked by a high ridge of chalk hills, running roughly between Dover and Calais. To the north would have been a freshwater lake, fed by rivers, and deepened over thousands of years.
The lake, hundreds of feet above sea level, finally overflowed the chalk ridge and swept down towards the Atlantic. The water washed away the soft chalk hills and left the British Isles a separate land mass.
Dr Gupta’s work is outlined in his book Homo Britannicus: the Incredible Story of Human Life in Britain, to be published next week.