Hundreds of thousands of years ago, one of the largest floods in Earth’s history turned us into an island and changed the course of our history. Britain was not always isolated from our continental neighbours. In the Pleistocene era, we were linked to France by a land ridge called the Weald-Artois anticline that extended from Dover, across what are now the Dover Straits.

This ridge of chalk separated the North Sea on one side from the English Channel on the other. For Britain to become an island, something had to have breached the ridge.

Now, Sanjeev Gupta and colleagues from Imperial College London have found firm evidence that a huge ‘megaflood‘ was responsible. They analysed a hidden series