Via a longtime reader, geologists have new evidence clarifying how Britain split off from the European mainland 450,000 YBP:
Researchers have found geological proof of one theory, that a catastrophic flood sparked massive waterfalls that cut through the rock ridge running through what's now the Dover Strait.
Analysis of [sonar] imagery, alongside existing supporting data, has led Collier and Gupta to report that Britain left Europe via a much more catastrophic route than erosion simply nibbling away at our connection to the continent. Instead, a glacial lake — perhaps sparked by an earthquake — over spilled its bounds in giant torrents of water.
"The waterfalls were so huge they left behind the plunge pools, some several kilometres in diameter and 100 metres deep in solid rock, running in a line from Calais to Dover," Collier said.
The chalky escarpment - similar to the cliffs at Dover - fell apart and released an epic flood, partially washing away the British land bridge to Europe.
That event wasn't enough to entirely separate the UK from Europe, with the final breach caused by a second megaflood that followed the first by as much as a hundred thousand years.
They conclude, "Had the initial flood not happened, the researchers added that Britain could still be connected to Europe, jutting out the same way Denmark does today."