Brexit actually happened 450,000 years ago, scientists find

Theresa May has repeatedly insisted that Britain is leaving the EU and not Europe – but she might be a few hundred thousand years too late

This is an illustration of what the land bridge connecting Britain to Europe may have looked like before the formation of the Dover Strait. The foreground is around where the port of Calais is today and way in the distance (the background of this illustration) is early Britain. Huge waterfalls cascading over the land bridge represents the beginning of physical separation of Britain from Europe (Imperial College London/Chase Stone)

Brexit might feel like it's been going on a while. But it's been 450,000 years in all, according to new research.

Scientists have shed new light on how ancient Britain separated from Europe, a movement that happened in two stages. The new research shows how exactly Britain left the European continent, before which the two had been stuck together.

And it also proves that the split was caused by a set of chance, unlikely circumstances. If that hadn't happened, Britain would continue to stick onto mainland Europe, jutting out in the same way that Denmark does today.

"The breaching of this land bridge between Dover and Calais was undeniably one of the most important events in British history, helping to shape our island nation's identity even today," said Professor Sanjeev Gupta, a co-author from the Department of Earth Science and Engineering at Imperial. "When the ice age ended and sea levels rose, flooding the valley floor for good, Britain lost its physical connection to the mainland. Without this dramatic breaching Britain would still be a part of Europe. This is Brexit 1.0 – the Brexit nobody voted for."

Theresa May has repeatedly stressed that the more contemporary Brexit will take two years and will see the country leave the European Union, but not Europe. That separation from the continent actually happened 450,000 years ago, it turns out.

Britain is thought to have separated from mainland Europe as a result of spill over from a lake, which formed in front of an ice sheet. Researchers have long believed that theory, but it has remained unproven – until the new research showed that the opening of the Dover Strait, which now houses the Channel Tunnel, happened in two episodes.

The new study, published in Nature Communications, shows how the chalk ridge that sits between Dover and Calais was breached. New data shows evidence of huge holes and a valley system on the seafloor.

Before Britain split from Europe, the chalk ridge acted as a huge dam, keeping the lake behind it. But the lake then overflowed in huge waterfalls, eroding the rock away until it broke and released huge amounts of water into the valley.

Later on – perhaps hundreds of thousands of years later – the Dover Strait was fully opened up. Other, smaller lakes in front of North Sea ice sheets spilled over and into a valley network between the two landmasses, separating the two entirely.

The work combines ten years of research to paint a picture of how the English Channel came to be flooded and create the original Brexit, splitting Europe from the British Isles.

"Based on the evidence that we've seen, we believe the Dover Strait 450,000 years ago would have been a huge rock ridge made of chalk joining Britain to France, looking more like the frozen tundra in Siberia than the green environment we know today," said Jenny Collier, a co-author of the study from the Department of Earth Science and Engineering at Imperial College London. "It would have been a cold world dotted with waterfalls plunging over the iconic white chalk escarpment that we see today in the White Cliffs of Dover.

"We still don't know for sure why the proglacial lake spilt over. Perhaps part of the ice sheet broke off, collapsing into the lake, causing a surge that carved a path for the water to cascade off the chalk ridge. In terms of the catastrophic failure of the ridge, maybe an earth tremor, which is still characteristic of this region today, further weakened the ridge. This may have caused the chalk ridge to collapse, releasing the megaflood that we have found evidence for in our studies."

The central evidence is the nature of the holes found on the bottom of the channel, which appear to have been caused by water plunging from the lake and into the valleys and then hitting the grond. Engineers first evidence of those pools when carrying out surveys of the seafloor in the 1960s, but researchers have gradually found evidence that they were caused by huge, ancient waterfalls.