London - From the shock vote to leave the European Union to key negotiations in Brussels and dramatic resignations by Foreign Secretary Boris Johnson and Brexit minister David Davis, here are some of the milestones on the path to Britain leaving the European Union:
- Britons vote for Brexit -
On June 23, 2016, 17.4 million Britons -- 52 percent vs 48 percent -- vote to end their 43-year-old membership of the EU.
The results show England and Wales voted to leave, while London, Scotland and Northern Ireland opted to remain.
Map showing how Britain voted in the Brexit vote
- Change of leader -
On June 24, Conservative prime minister David Cameron, who called the referendum and led the remain campaign, announces his resignation, sparking a leadership race.
Brexit campaigner Boris Johnson withdraws at the last minute and Theresa May, Cameron's interior minister for six years, is crowned leader on July 11.
- Clean break -
On January 17, 2017, May gives a major speech setting out her Brexit strategy.
She had previously promised to cut EU migration and now acknowledges this means Britain would also leave Europe's single market.
She warns she is willing to walk away from the negotiations, saying: "No deal for Britain is better than a bad deal for Britain."
- Parliament backs Brexit -
On March 13, Britain's parliament gives final approval to a bill empowering May to trigger Article 50 of the EU treaty, which lays out the process for leaving the EU.
Amendments passed by the House of Lords to guarantee the status of European nationals living in Britain and to give parliament a vote on the final deal are overturned and the bill passes unchanged.
- Article 50 -
The government triggers Article 50 on March 29 in the form of a letter to EU President Donald Tusk, starting a two-year timetable until withdrawal on March 29, 2019.
"We are on the threshold of the most important negotiation for this country for a generation," Brexit minister David Davis says.
- Lost majority -
In a bid to capitalise on the perceived weakness of the main opposition Labour party and strengthen her hand in Brexit negotiations, May calls a snap election for June 8.
Her gamble backfires spectacularly as the Conservatives lose their parliamentary majority. They are forced to strike a deal with Northern Ireland's Democratic Unionist Party (DUP) to be able to govern.
- Florence speech -
In a keynote speech in Florence, Italy on September 22, May outlines plans for a two-year transition period after Brexit and says Britain will continue its EU budget contributions during that period.
Britain's contributions over the two years after its departure would be about 20 billion euros ($24 billion), an amount judged well short of the figure deemed necessary by EU officials.
The government later agrees to increase the figure to an unspecified amount, reportedly up to 55 billion euros.
- Irish row -
The issue of British guarantees to keep an open border between Northern Ireland and the Republic of Ireland after Brexit becomes a key sticking point.
On December 4, May is on the cusp of an agreement but the DUP scuppers the deal at the last minute, saying it was not consulted in time.
DUP leader Arlene Foster calls the proposed agreement a "big shock" and says there should be "no regulatory divergence" between Northern Ireland and the rest of Britain.
Map showing the impact of the Irish border on the Brexit negotiations
- Deal in Brussels -
Britain and the EU reach a historic deal on the terms of the Brexit divorce in early December after all-night negotiations and an early-morning dash to Brussels by May.
EU leaders give the go-ahead for the next stage of Brexit negotiations to begin, agreeing there has been sufficient progress.
- Brexit bill passed -
A bill enacting the decision to leave the EU becomes law on June 26, 2018, following months of debate, after being given the formal royal assent by Queen Elizabeth II.
The bill transfers decades of European law onto British statute books and also enshrines Brexit day in British law as March 29, 2019.
- Two key resignations -
In a major blow to the prime minister, Johnson followed Davis in resigning over her masterplan to retain strong economic ties to the EU after leaving the bloc.
The resignations come days after the cabinet agreed on a compromise deal in a bid to unblock negotiations with Brussels -- a plan Davis says would "make the supposed control by Parliament illusory".