Hundreds of thousands of years ago, ancient Britain split up from the rest of Europe. It was, as scientists say, the original Brexit -- a separation that was brought about not by political and societal factors, but natural geologic events that new evidence now sheds light on.

According to a report from BBC News, researchers from the Imperial College London and other institutes in Europe have worked out how a strip of land that used to connect Britain to Europe was snuffed out.

Specifically, this stretch of land linked Dover in the south of England to Calais in the north of France. A large lake located in the north of this strip likely overflowed 450,000 years ago to the land, causing erosion and damaging it. Later, another flood opened the Dover Strait.

Large underwater holes discovered a few decades ago in the depths of the English Channel support this series of events. Analysis of the mysterious holes showed that they were most likely caused by the lake spilling over.

Study leader Sanjeev Gupta of the Imperial College London described the holes as isolated depressions occurring in a line. The underwater holes were measured as 100-meter deep and hundreds of meters to several kilometers in diameter.

"So we interpret these as giant plunge pools," Gupta explained. "We think there was basically lake water plunging over this rock ridge in the Dover Strait through a whole series of waterfalls, which then eroded and carved out these depressions. It's difficult to explain them by any other mechanism."

Aside from the massive lake spilling over, the researchers believe that a second flood occurred to completely destroy the land bridge 150,000 years ago and create the Straits of Dover. Gupta pointed out that the valley through the strait exhibit qualities consistent with flood erosion.

The team isn't certain about the cause of these events. Possibilities are earthquakes or part of the ice sheet breaking off into the lake.

There may be more than what the team hopes to achieve in this study -- they're hoping to figure out the precise timing of the "geological Brexit" next -- but they're also convinced that these events shaped the British psyche in a significant way.

"You know, there's something in the British psyche about this island state that's very important to us," co-author Jenny Collier told Gizmodo. "We are part of continental Europe, but in terms of history, this did mark the point of our physical isolation. The Straits of Dover have an iconic meaning to the British throughout time."

The researchers published their findings in the journal Nature Communications.