” . . . 8,500 BC - when Britain was part of continental Europe.”
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Around 10,000 years ago, during the Devensian glaciation with its lower sea level, Great Britain was not an island, but an upland region of northwestern Europe, lying partially underneath the Eurasian ice sheet. The sea level was about 120 metres (390 ft) lower than today, and the bed of the North Sea was dry and acted as a land bridge to Europe, now known as Doggerland. It is generally thought that as sea levels gradually rose after the end of the last glacial period of the current ice age, Doggerland became submerged beneath the North Sea, cutting off what was previously the British peninsula from the European mainland by around 6500 BC