LONDON (AFP) - From the shock Brexit vote to a tentative deal on the outlines of a withdrawal agreement, here are the milestones on Britain's rocky road out of the European Union.

Britons vote to leave

In a referendum, Britons on June 23, 2016, choose to end their membership of the EU by 52 per cent to 48 per cent.

The shock result prompts the resignation the next day of Conservative prime minister David Cameron, who had called the referendum and led the campaign to remain in the EU.

In a race to replace him, Brexit campaigner Boris Johnson withdraws at the last minute and Theresa May, Cameron's interior minister for six years, becomes prime minister on July 11.

Clean break

On Jan 17, 2017, May gives a major speech setting out her Brexit strategy, saying Britain will also leave Europe's single market.

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 union.

Exit process triggered

With a letter to EU President Donald Tusk on March 29, formally announcing the intention to leave, the government sets in motion Article 50.

Its two-year timetable for withdrawal is set to wind up by March 29, 2019.

Lost majority

To capitalise on the perceived weakness of the opposition Labour party and strengthen her hand in Brexit negotiations, May calls a snap election for June 8.

Her gamble backfires 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.

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 in negotiations.

First terms agreed

Britain and the EU reach a deal on some key terms of the divorce in early December 2017 after all-night negotiations. They include Britain's EU bill as part of the settlement.

EU leaders give the go-ahead for the next stage of Brexit talks, including on how Britain will continue to trade with the bloc after the split.

Brexit Bill passed

A Bill enacting the decision to leave the EU becomes law on June 26, 2018, following months of debate and after receiving the formal assent of Queen Elizabeth II.

The Bill transfers decades of European law onto British statute books and enshrines "Brexit day" as March 29, 2019.

Top minsters quit

On July 6, May wins agreement from her warring Cabinet to pursue "a UK-EU free trade area" that would retain a strong alignment with the EU after Brexit.

Two days later David Davis, the eurosceptic Brexit minister, quits as does his deputy. May is giving "too much away too easily", Davis says.

In a major blow, Foreign Secretary Boris Johnson also resigns on July 9, having criticised the Brexit blueprint in private, and becomes a leading critic of May's plans through a weekly column in the Daily Telegraph newspaper.

Britain says draft deal agreed

The European Union on Nov 13 publishes contingency plans for a "no-deal" Brexit.

But a few hours later, May's office says negotiating teams in Brussels have reached a draft agreement, which will be considered by the Cabinet on Nov 14.

Cabinet approval

After a more than five-hour meeting on Nov 14, May says the British cabinet had made a "collective decision" to back the draft deal.