Ten years ago, Britain made a decision that would transform its politics, redefine its relationship with Europe and usher in one of the most turbulent periods in modern British history.
On 23 June 2016, voters chose to leave the European Union by a margin of 52% to 48%, ending more than four decades of membership in the bloc. What followed was years of political upheaval, constitutional clashes, leadership changes and bitter national debate over Britain's future.
The referendum itself was the culmination of a long-running argument over Britain's place in Europe. Under pressure from eurosceptic lawmakers and the rising UK Independence Party, Prime Minister David Cameron promised a referendum on EU membership if his Conservative Party won the 2015 election.
When voters backed Brexit, Cameron resigned within hours of the result, saying the country needed new leadership for the next stage of the process.
His successor, Theresa May, inherited the task of delivering a departure that many had voted for but few had clearly defined.
In March 2017, May formally triggered Article 50, launching the countdown to Britain's exit. What appeared straightforward in principle quickly became mired in political and legal complexity.
Negotiations with Brussels were dominated by questions over trade, citizens' rights, Britain's financial obligations and, above all, the Irish border. The challenge of avoiding a hard border between Northern Ireland and the Republic of Ireland became one of the most contentious issues in the talks.
At home, divisions deepened.
Seeking to strengthen her hand, May called a snap election in 2017. Instead, she lost her parliamentary majority, weakening her authority at a crucial moment. As negotiations dragged on, opposition mounted from both Brexit supporters who believed she was making too many concessions and pro-European lawmakers seeking closer ties with the EU.
Parliament rejected May's withdrawal agreement three times in early 2019, producing scenes of unprecedented political deadlock. Brexit deadlines came and went as European leaders granted extensions to prevent a chaotic departure.
Outside Westminster, public frustration spilled onto the streets. Pro-Brexit campaigners demanded Britain leave immediately, while supporters of a second referendum organised some of the largest political demonstrations seen in Britain for decades.
The stalemate proved fatal for May's premiership.
Fighting back tears outside Downing Street in May 2019, she announced her resignation, saying it had been the honour of her life to serve as prime minister.
Her successor, Boris Johnson, arrived promising to end the paralysis.
Campaigning on the slogan "Get Brexit Done", Johnson pledged Britain would leave the European Union by the end of October 2019. His efforts triggered a constitutional confrontation when he moved to suspend Parliament amid fierce disputes over Brexit strategy.
The decision sparked protests across the country and was later ruled unlawful by Britain's Supreme Court, which declared that Parliament had never legally been suspended.
Despite the controversy, Johnson secured a revised withdrawal agreement with the European Union and called a snap general election.
The December 2019 vote proved decisive.
The Conservatives won a commanding majority, giving Johnson the parliamentary numbers needed to push Brexit legislation through Parliament and break years of deadlock.
On 31 January 2020, Britain formally left the European Union.
In Parliament Square, Brexit supporters gathered beneath countdown clocks as crowds cheered and waved Union flags. Elsewhere, opponents marked the moment with sadness, viewing it as the end of a political and economic partnership that had shaped Britain for generations.
Yet leaving the EU was only the beginning.
The Political Cost
Throughout 2020, negotiators raced to agree the terms of a future relationship before the transition period expired. Disputes over fishing rights, trade rules and customs arrangements fuelled fears of a no-deal rupture that could damage economies on both sides of the Channel.
As lorries queued near the port of Dover and businesses prepared for sweeping changes, negotiators worked against the clock.
Just days before the deadline, Britain and the European Union reached a trade agreement. On 30 December 2020, the deal was signed in London and Brussels, paving the way for a new chapter in UK-EU relations.
When the transition period ended at midnight on 31 December, Britain completed its departure from the EU's single market and customs union.
The years that followed brought new debates over trade, migration, regulation and economic growth. Brexit remained a defining issue in British politics even as other crises — including the pandemic, inflation and geopolitical tensions — competed for attention.
The political turbulence unleashed by the referendum also reshaped Britain's leadership. Since the Brexit vote, the country has cycled through a succession of prime ministers, highlighting the challenges of governing a nation still divided over the consequences of leaving the European Union.
A decade on, supporters regard Brexit as the restoration of national sovereignty and democratic control. Critics argue it has created economic and political costs that continue to be felt.
What is beyond dispute is its historical significance.
What began as a referendum promise evolved into a political transformation that changed governments, tested institutions and altered Britain's place in the world. Ten years later, the arguments it unleashed continue to shape the country's future