Expert: How ancient Brexiteers cut ties with Europe to build our most mysterious monuments

Thousands of years ago, while the rest of Europe embraced metal tools and wheeled carts, people in the British Isles decided to go it alone.

Around 3000 BC, the Neolithic farmers who would later build iconic monuments like Stonehenge apparently turned their backs on European neighbours - choosing isolation instead of innovation.

Cutting themselves off from continental Europe - just like modern day Brexiteers - why did these prehistoric Britons simply want to be left alone?

"For reasons that we're just beginning to glean, Britain cut itself off from the continent," said Parker Pearson, speaking on the HistoryExtra podcast.

At this stage, Europe was in the midst of a technological boom. Communities across the continent were discovering metallurgy - making tools and weapons - and creating wheeled carts to make life easier.

Yet across the Channel, prehistoric Britons weren't interested. "They were not plugged into the exchange networks of the whole of Europe," Parker Pearson explained. "Given that metallurgy was available, given that knowledge of the wheel was also there on the continent, they were just blocking off all these potential innovations."

The evidence supports this theory. Pottery styles, burial practices and architecture in Britain all diverged sharply from those on the continent. "We can also see that there's absolutely no traded material going either way across the channel," Parker Pearson adds. "The traditions that developed in Britain were completely different, both in architectural [terms] and [in] small items like pottery."

Despite this isolation, Late Neolithic Britons created some of the most famous and mysterious monuments in history - including Stonehenge and other huge stone circles and henge enclosures.

"It's within that period of isolation that they built Stonehenge and other major stone circles," Parker Pearson says. "As well as the big henge enclosures - circular, ditched and banked structures." He adds that these "are styles that are entirely restricted to the islands of Britain and Ireland."

This Late Neolithic period was defined by ritual and ceremony, not technological progress. Key sites like Stonehenge, Avebury in Wiltshire and Newgrange in Ireland became hubs for feasts, seasonal gatherings and spiritual observances.

But these people weren't city dwellers. "It's a community that is also without villages," Parker Pearson explains. "We have just single farmsteads scattered across southern Britain, and there are key places - centres for ceremonial and monumental activity."

They weren't stuck in one place either. "People were not quite nomadic, but highly mobile," he adds. "They were living in different places at different times of the year, moving with their animals - their cattle and their pigs - to be at the ceremonial centres for particular times of year, for feasting."

This isolation lasted until around 2500 BC, when the Beaker people arrived in Britain from Europe.

Named after their distinctive bell-shaped pottery, the Beaker people brought new metal-working techniques, individual burials and new genetic ancestry.

"Within some 16 generations of the initial Beaker arrival, we're seeing the very large replacement of the gene pool," Parker Pearson says. "The population - 400 years later, 16 generations later - they've really got only about 10% of that British farmers' DNA in their genome."

The Beakers transformed Britain, bringing it back into Europe's sphere of influence and ushering in the Bronze Age.

But why did Britain cut itself off for so long before then? "We don't have any idea," Parker Pearson concedes - though new findings in ancient DNA offer one possibility: plague.

"One of the really interesting results we're getting from DNA analysis is that we can see episodes of Bubonic Plague," he says. The deadly bacteria, Yersinia pestis, has been found in the teeth of people buried in Neolithic Britain.

"We know that there were at least two cases of Bubonic Plague in Britain," Parker Pearson explains. "One [occurred] before the Beaker people even arrived - around 2900-2800 BC, so about four centuries earlier. And then we've got a second event some 300 years after their initial arrival," seen in remains "from burials in different parts of Britain."

That discovery raises troubling questions. "It is possible that we are just seeing the tip of the iceberg," Parker Pearson says, "and that the whole point about these large-scale migrations is that they act as a vector for the spreading of diseases across the whole continent."

If so, Britain may have isolated itself to stop infections spreading - long before the Beaker people reconnected Britain to Europe and kickstarted a new era.

For three centuries before their arrival, Britain stood alone - independent, inward-looking and fiercely original. Its communities left a cultural legacy that still shapes our history and imaginations today.