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. Here is what we know so far, following Tuesday's ruling by the Supreme Court that Prime Minister Theresa May must seek parliamentary approval before she can start Brexit negotiations. Referendum: On June 23, 2016, Britons voted by 52 percent in favour to 48 percent against leaving the EU, although most voters in Scotland, Northern Ireland and London backed remaining part of the bloc. 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 and stem the rise of the UK Independence Party (UKIP) but his campaign to stay in the EU failed. He resigned hours after the referendum results came in. Timing: 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. The government has said this timetable will not change even though the Supreme Court ruled Tuesday that parliament will have to first pass a bill authorising May to begin Brexit negotiations. 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 by 2018, ahead of the 2019 European Parliament elections. Parliament: Lawmakers are widely expected to give their go-ahead for the government to begin Brexit talks, although the main opposition Labour Party has said it wants to table amendments to the proposed legislation. This could, in theory, delay the start of Brexit. Most MPs supported Britain staying in the EU but many have said they will now respect the result of the referendum. The government has said it expects no change and has already prepared draft legislation. 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. Transition deal: 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. Immigration: 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. May has given no detail of what the new entry criteria will be for Europeans and 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. Trade: 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 has said full customs union membership would prevent Britain from striking its own trade deals with other countries but said the nation could remain a signatory to some parts of the customs union. May has 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 has 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.
