Britain is set to become the first European Union member to leave the bloc following a referendum last year in which a majority voted for Brexit.
Prime Minister Theresa May has said Britain would leave the EU’s single market and seek a new customs deal with the bloc.
But the precise timings and terms of departure are uncertain as negotiations have yet to begin.
Here is an outline of what we know so far:
On June 23, 2016, Britons voted by 52 per cent in favour to 48 per cent against leaving the EU, although most voters in Scotland, Northern Ireland and London backed remaining part of the bloc.
Britain has had a love-hate relationship with Brussels since joining what was then the European Economic Community in 1973.
Former prime minister David Cameron, who took office in 2010, called the referendum in a bid to end long-standing divisions in his Conservative party but his campaign to stay in the EU failed.
Cameron’s successor May has said she wants to trigger Article 50 — the formal procedure for leaving the EU under the Lisbon Treaty — by the end of March.
Finance minister Philip Hammond has said he expects negotiations to begin before the summer.
Article 50 foresees a maximum two-year time period for the negotiations.
If no deal is in place by then, Britain would have to leave without any agreement on future ties with the EU, unless the timeframe can be extended by unanimous agreement of all member states.
The EU’s top Brexit negotiator Michel Barnier has said there should be an agreement in place ahead of the 2019 European Parliament elections.
Britain’s Supreme Court will rule on Tuesday whether or not May must receive parliamentary approval before triggering Article 50.
If the court rules against the prime minister, ministers would likely bring draft legislation backing her timetable before the House of Commons and House of Lords.
Most MPs supported Britain staying in the EU but are expected to back the start of Article 50 talks — although her opponents could table amendments to try to bind her hands.
May has also promised that any final deal on Britain’s future relations with the EU would go before both chambers of parliament for a vote.
In a major speech on January 17, May said she wanted a “phased approach” to ensure stability for businesses between the moment Britain leaves the EU and the implementation of its new relationship with the bloc.
“We will seek to avoid a disruptive cliff edge,” she said.
May added that all existing EU laws that apply in Britain will be turned into British laws under a “Great Repeal Bill” and parliament will then be able to choose which ones to keep, reject or amend.
May has said she will make cutting immigration a priority in negotiations, after the issue dominated the referendum campaign.
Hundreds of thousands of people, mainly from eastern and southern Europe, move to Britain each year.
In her Brexit speech, she gave no detail of what the new entry criteria will be for Europeans, but acknowledged that this demand would mean Britain leaving the EU’s single market.
May has refused to confirm that EU citizens already in Britain can stay after Brexit until similar guarantees are offered to Britons living elsewhere in the bloc.
May said she wants “maximum possible access” for British companies to the single market even though Britain will not be a member, and also called for a new customs arrangement with the EU.
She said full customs union membership would prevent Britain from striking its own trade deals with other countries but said the country could remain a signatory to some parts of the customs union.
May also warned EU member states against pushing for harsh exit terms for Britain, saying it would be “an act of calamitous self-harm” for the EU.
She threatened that she could “change the basis of Britain’s economic model” — for example by slashing business taxes — if British companies were excluded from accessing the single market.