Leaving the EU: How Britain got here and what comes next

TODAY, Theresa May, Britain’s prime minister, will deliver a letter to Donald Tusk, the president of the European Council, to officially trigger Article 50 of the Treaty of Lisbon. That will start a two-year clock for the difficult negotiations over the terms of Britain’s divorce from the European Union. Once time runs out, Britain will likely leave the club—deal or no deal.

For decades, Britons had told pollsters they were dissatisfied with the EU. And although Euroscepticism has been particularly high in recent years, according to the British Social Attitudes Survey, most respondents tended to say they had not thought seriously about severing ties with the EU. As a result, British politicians did not devote much consideration to the idea either. The tide only began to turn once the UK Independence Party (UKIP), whose defining issue was separation from the EU, began to threaten support for the ruling Conservatives. In 2013 the Tories promised that if they won a majority at the next election, they would hold an in-out referendum on EU membership. That was enough to quell most conflicts within the party and quash UKIP’s surge. But a surprise majority victory in the 2015 general election forced David Cameron, then the prime minister, to deliver on his pledge. A divisive campaign on Britain’s EU membership followed, resulting in a slim victory for the Leave camp on June 23rd 2016.

The two-year deadline set for Britain′s departure will be hard for negotiators to meet. Any agreement needs the approval of 65% of EU member states before it is presented to the European Parliament for ratification. Worse still, an extension of this tight timetable would require the unanimous consent of the remaining 27 countries.

The slew of elections scheduled in continental Europe in the coming months will make the task of reaching an agreement on time even more difficult—both because candidates will want to ensure voters they will not give Britain a sweetheart deal, and because changing governments could cause member states to change their positions. For example, France will hold its presidential election next month. The German federal ballot is scheduled for September, and Italians will go to the polls in May 2018.

Even in the months following the referendum, Brexit still seemed like a vague and distant prospect. It is now set to become a reality—and quite possibly a messy one.

For more details on the Brexit process read our explainer.