The first Brexit happened a very long time ago. According to Richard Webb in Brexit, 10,000 BC: The untold story of how Britain first left Europe (New Scientist), the white cliffs of Dover did not exist 450,000 years ago, just rolling hills. However, as usual, there was an ice age, and a glacial lake was formed in what is now the North Sea:
The lake was well above sea level to the southwest. The barrier, then made of bedrock, broke, and a volume of water similar to the present North Sea gushed through in a matter of two weeks, gouging out a large channel.
Subsequently during the ice ages which predominated and during the short interglacials Britain was still part of the continent of Europe.
Then 180,000 years ago, the same thing happened, although this time the barrier consisted of alluvial sediment rather than bedrock, so the lake did not grow to the same proportions before producing a gusher:
Ice ages then resumed which can lower the sea as much as 120 metres below today’s level, so most of the time you could have walked across with little difficulty until the Holocene, with the exception of the Eemian interglacial, when sea levels were 6-9 metres higher than now. So 125,000 years ago Britain was cut off in the first real Brexit. After the Eemian the ice sheet returned, and Britain was again attached to Europe. The Neanderthals who arrived about 60,000 years ago did not need a boat. Nor did Homo Sapiens who appeared around 40,000 years ago.
Between 20,000 years ago and 10,000 years ago, with the onset of the Holocene, there was serious warming and sea level rise but still Britain remained attached:
The final exit came with the ‘Norway solution’ around 8,200 years ago. Here’s the transition:
- By 9000 years ago, the world was considerably warmer and the sea was pushing its way back up through the Strait of Dover. To its north, there was still dry land. Known as Doggerland after the Dogger Bank, a sandy feature on the bottom of today’s North Sea, its pleasant, wooded valleys and meandering rivers would once have been a paradise for the stateless hunter-gatherers of the period. As the planet warmed further, the area became wetter and marshier, a low-lying lagoon archipelago.
The coup de grâce, 8200 years ago, was dramatic. An undersea earthquake triggered huge submarine landslides off the coast of Norway, known as the Storegga slides. They dislodged something like 3000 cubic kilometres of material, and created a huge tsunami that raced across the North Sea. Whatever was left of Doggerland didn’t stand a chance, overwhelmed by waves 5 metres high. Once again, the land bridge that connected Britain with Europe was washed away. For a third time, water rushed through the Strait of Dover – and Britain was left in glorious isolation again.
From then onwards, Britain has been free:
The above story is a simplification. The full story includes the reshaping of coastlines around the area. It does require verification and pinning down of the exact dates by a drilling program, which is expensive. Money had recently been secured, from the EU, but the project failed for want of a decent drilling boat. With economic and political Brexit, the project will be harder to revive.
As a related story, early hominins, possibly Homo antecessor, arrived in proto-Britain sometime before 800,000 years ago. Hominin footprints and stone tools have been found at Happisburgh, now on the Norfolk coast, some 200 kilometres north of Dover. These footprints are the oldest found outside Africa. The environment would have been harsh, but hominin presence persisted until 250,000 years ago.
As to the future, the greenhouse emissions caused modern Homo sapiens have ensured that the scheduled return to ice age conditions has been cancelled and Britain will remain forever free, and alone if it so chooses.