A flood of epic proportions separated Britain from mainland Europe some 200 000 years ago, according to a recent sonar study of the English Channel floor, the BBC reported.
The study shows deep furrows on the chalk bed of the channel, cut by months worth flooding water from a massive lake in what is now the North Sea.
Nearly one million cubic meters of water were discharged in that period, eroding the Weald-Artois ridge isthmus that linked Britain to continental Europe.
It's not cleared what caused the water breaking through, although the team of scientists that conducted the study believe it was either the build-up of water in the lake or a minor earthquake, which are not unheard of in the south of Britain.
"This event, or series of events, that caused [the breach] changed the course of Britain's history," said Sanjeev Gupta, one of the scientists working on the project.
The study is the most conclusive evidence yet supporting the megaflood theory, which has been around for decades.