It's been three years since the United Kingdom voted to leave the European Union, and in the ensuing period, the debate about how exactly to leave has claimed a prime minister, several MPs and the parliamentary majority of the ruling Conservative Party.

Key points: Leading Brexiteer figures were peers at Eton College, an elite school established in 1440

Leading Brexiteer figures were peers at Eton College, an elite school established in 1440 All post-war PMs who attended university did so at Oxford, except for Gordon Brown

All post-war PMs who attended university did so at Oxford, except for Gordon Brown Critics of some Brexiteers say their privilege distances them from seeing its impact

The Brexit decision, which some have billed as a populist revolt against an out-of-touch elite, is now in the hands of Alexander Boris de Pfeffel Johnson — a man who campaigned for Brexit in the run-up to the 2016 referendum, and whose origins were steeped in the institutions of Britain's elite.

Mr Johnson was a classmate of David Cameron at Eton College — a world-renowned boarding school, which has produced 20 British prime ministers overall, with five taking the top job since World War II.

Admitted to Eton as an academic high-achiever as a King's Scholar, the young Johnson went on to hold leading positions at the school. Later, as an undergraduate at Oxford University, he became president of its centuries-old debating society, the Oxford Union.

Just under half of Mr Johnson's cabinet are Oxbridge graduates. ( AP: Stefan Rousseau, pool )

Of course, this political lineage is part and parcel of British politics, considering Westminster is home to a significant number of MPs who have either gone to elite boarding schools or Oxford and Cambridge universities.

But now, as Britain's scheduled exit from the EU is due to happen in exactly three weeks' time with or without a trade deal, a select group of politicians are destined to make a decision that will have ramifications for Britons across the union.

This has led others to speculate about whether or not Brexit has actually always been the project of a storied political elite to begin with.

"[Brexiteers] are the 'Little Englanders' who have tried to portray themselves as outsiders," Robert Verkaik, author of the book Posh Boys: How English Public Schools Ruin Britain, told the ABC.

"[But they] very much are insiders and a product of the establishment."

Understanding Brexit involves understanding Eton

Eton has taught several British Prime Ministers and Princes William (pictured) and Harry. ( Reuters: Dylan Martinez )

Days after the Brexit referendum vote in 2016, Financial Times columnist Simon Kuper last noted that the decision wasn't simply "an anti-elitist revolt".

"Rather, it is an anti-elitist revolt led by an elite — a coup by one set of public schoolboys against another," he wrote at the time.

In British parlance, 'public school' refers to the independent boarding schools that stretch back centuries — home to global royalty, and the offspring of political and business leaders.

The names of some of those involved in Brexit belong to numerous graduates from public schools.

Fellow Eton graduates include former prime minister David Cameron; arch-Brexiteer — and current House of Commons leader — Jacob Rees-Mogg; founding partners of Cambridge Analytica's parent company Nigel and Alex Oakes; Cambridge Analytica's former CEO Alexander Nix; and a number of Conservative Party MPs.

Those on the pro-Remain side of the ledger are also old-Etonians, which includes the deputy chair of the People's Vote campaign, Hugo Dixon, and Labour peer Lord David Sainsbury, who contributed over 4 million pounds ($7.3 million) to Remain-aligned campaigns in the lead-up to the 2016 referendum.

Verkaik said one reason for Eton's share of Brexiteers was because of the school's long-standing role in Britain's imperial history.

Old Etonians involved in Brexit include Clockwise L–R, Nigel Oakes, Alexander Nix, Boris Johnson, Jacob Rees-Mogg, Jo Johnson, Lord David Sainsbury, David Cameron and Rory Stewart. ( ABC News: Jarrod Fankhauser )

The school was founded in 1440 by King Henry VI, which had an original remit to educate poor boys, but over subsequent centuries, it became a breeding ground for generations of English, and later Imperial leadership.

By the 1800s, there were very few poor boys attending schools like Eton, when, according to Verkaik, it became a place for, "bastions of influential upper-class elites who were in control of Britain and its empire".

"There was a direct link between the schools, the government, and the Empire."

He suggested schools such as Eton taught histories of Britain that presented a positive view of its imperial history, where Empire was seen as "giving to the world rather than taking away from it".

Eton student were even obliged to wear top-hats during WWI training in 1915. ( Supplied: National Archive Netherlands )

He also suggested the school years of prime ministers David Cameron and Boris Johnson coincided with a small "romantic surge" of British imperialism due to the 1982 Falklands War.

"I imagine it would've affected Mr Johnson and his class because this was a moment when values relevant to public schools were being played out again — Britain was re-establishing its military prominence," Verkaik said.

British author — and fellow 1980s Eton graduate — James Wood suggested in the London Review of Books that this effect was evident, as he claimed it was a "cabal of old Etonians born between 1962 and 1975" that had "carefully instituted, secretly engineered and noisily bolstered" Brexit.

"In 1984, I couldn't have predicted politics in the early 21st century would be dominated by my schoolfellows".

After Eton, it's time to get acquainted with Oxbridge

Oxford University has produced 11 British Prime Ministers in the post-war period. ( Flickr: Tejvan Pettinger )

Since World War II, of the British prime ministers who did attend university, only one, Gordon Brown, was educated at a university other than Oxford.

By the time Boris Johnson took the prime ministership in July this year, he became the 11th Oxford graduate to join the exclusive club.

"You turn the pages of yellowing student newspapers from 30 years ago, and there they are, recognisably the same faces that dominate today's British news. Boris Johnson running for Union president, Michael Gove winning debating contests, Jeremy Hunt holding together the faction-ridden Oxford University Conservative Association (OUCA)," Kuper wrote.

About 45 per cent of Mr Johnson's cabinet are graduates of Oxford and Cambridge universities (commonly referred to as Oxbridge), with almost two-thirds having been educated at private schools, according to data from the Sutton Trust — a British organisation researching the country's social mobility.

Eton has been responsible for 20 British prime ministers since the position came into being. ( ABC News: GFX by Jarrod Fankhauser )

Rebecca Montacute, a research fellow at the Sutton Trust, told the ABC that consequently this concentration reflected a narrow picture of Britain within Westminster.

"[Because] you're getting so many similar experiences and voices around the table, there are large parts of British society you're not hearing from properly," Dr Montacute said.

A June 2019 report from the Trust and Britain's Social Mobility Commission looked into the backgrounds of 5,000 Britons in high-ranking positions, and found Oxbridge graduates made up a quarter of those surveyed.

Oxbridge graduates surveyed made up 71 per cent of senior judges; 57 per cent of former British prime minister Theresa May's cabinet; and 51 per cent of all diplomats.

Indeed, one of the earliest campaigns to get Britain out of the EU started at Oxford, when Oxford-graduate-turned-politician Daniel Hannan founded the Oxford Campaign for an Independent Britain in 1990.

Dr Montacute said British politics' over-recruitment from certain backgrounds, including a reliance on Oxbridge, has had real-world consequences.

"There have been criticisms that policies haven't been well-designed because the people making them have no idea how they will work on the ground," she said.

She added it "was a real issue" when policy makers had no idea how policies would impact on people at the design stage.

However, both Oxford and Cambridge universities have attempted to diversify their student bodies, with announcements to boost student intake from under-represented or disadvantaged backgrounds.

'Post-Brexit isn't going to affect them'

A no-deal Brexit runs the risk of critical medicine shortages for patients across the UK. ( Reuters: Peter Nicholls )

In 2019, perhaps the most consequential suite of British policies to happen since the end of World War II will be associated with Brexit.

So far, it is unclear if it will leave with a negotiated exit trade deal — thrice voted down in the House of Commons — or crash out without one. The latter may cause shortages of drugs and food, a spike in tensions on the Irish border, and a drop in British GDP by 2 per cent, according to the UK Office for Budget Responsibility.

According to data commissioned by British poverty-reduction charity the Joseph Rowntree Foundation, the poorest fifth of the UK's population could see their annual cost of living rise by 480 pounds ($875) in the event of a no-deal Brexit, owing to trade barriers and the increased prices of everyday consumer goods.

But, one of Brexit's last sticking points is its consequences for people on either side of the Irish border, where both Westminster and Brussels are trying to avoid a hard border between Northern Ireland and the Republic to avoid provoking sectarian tensions between British loyalist and Irish nationalist communities.

The original Brexit deal's proposal of an Irish backstop — where Northern Ireland would remain within a customs union with the EU — has been ruled out by Mr Johnson's Cabinet and has been consistently opposed by Northern Ireland's largest political party, the Democratic Unionist Party (DUP).

Instead Mr Johnson, this week, has proposed a common regulatory zone across the island of Ireland that Northern Ireland would have to approve every four years, which would allow the territory to leave the EU's customs union along with the rest of the UK.

However, Northern Ireland's devolved Parliament has not sat for over two years, and critics of Mr Johnson's plan say it has the potential to bring back hard-border infrastructure, which the Irish Government has ruled out — in recent days, Downing Street has reportedly said Mr Johnson's deal is "essentially impossible".

So, while it remains to be seen if Mr Johnson will be able to snag a deal with the EU in Brexit's final act, what may be certain will be the ability for Britain's political elite to execute their post-Brexit vision of Britain with little consequences, according to the London Review's James Wood.

"Whatever happens in the next 30 or 40 years, post-Brexit, isn't going to affect them," Wood wrote.

"Privilege is like an unwritten constitution: you can never lose what you never have to find."

Eton College and the Office of the Prime Minister were contacted for comment but did not respond to the ABC's requests.

Editor's Note — October 11, 2019: An earlier version of this story said Boris Johnson was the president of Oxford University's student union. He was actually president of the Oxford Union, which is the university's debating society.