Brexit has officially been triggered. What comes next?

After 44 years, Britain is officially leaving the European Union. Its relationship with the bloc is set to change, but the road map still remains to be laid out.

On Wednesday, Britain’s EU envoy, Tim Barrow, hand-delivered a letter from Prime Minister Theresa May to European Council president Donald Tusk in Brussels. The letter informs the European Council, the body representing national leaders, that the United Kingdom intends to withdraw from the bloc, triggering the Article 50 withdrawal process.

After the letter was delivered, Ms. May spoke to the House of Commons in Westminster, laying out her goals for the future, expressing her belief that Britain and the EU can work together to strike a fair deal for everyone. Echoing a theme that has been prominent since the June Brexit vote, she called on lawmakers to unite as the United Kingdom begins this “momentous journey.”

"[N]ow that the decision has been made to leave the EU ... it is time to come together," May said.

In June, Britain voted 52 percent to 48 percent to leave the EU. Most of Parliament, including then-Prime Minister David Cameron, was opposed to the measure. When Mr. Cameron resigned after losing the vote, May – who had also originally supported remaining in the EU – committed as prime minister to carrying out the will of the people as expressed in the referendum. In January, the Britain's Supreme Court ruled that Parliament needed to approve Brexit, which they did in March.

Wednesday marks the start of a two-year negotiating process, during which Britain will attempt to forge a deal that will grant it special status within the EU, May said. If negotiations take longer than that, a transitional arrangement could also be instituted, though May said she aims to have everything resolved inside the two-year window.

Within 48 hours of receiving the letter, Mr. Tusk will send the remaining 27 EU member states draft negotiating guidelines. Ambassadors from these states will then meet in Brussels to discuss the draft. On Thursday, May’s government will also publish a white paper addressing how EU law will be meshed with British law, she said in her statement.

Going forward, May said, the British government will seek to control immigration but maintain trade ties, in line with the wishes of British voters. But, she noted, access to the single market hinges on accepting free movement of people, as well as other freedoms.

“As accepting those freedoms is incompatible with the democratically expressed will of the British people, we will no longer be members of the single market,” May said.

Though the EU is not keen to see the UK leave, it said it is ready to move forward. The focus, the European Council said in its initial response to May’s letter, will be on preserving the EU’s interests and minimizing uncertainty for “our citizens, businesses and member states.”

But getting a deal is unlikely to be straightforward. 

Other EU member states, concerned about populist impulses across the continent, may be unwilling to offer Britain an appealing path to exit. Too good a deal, they say, could prompt other countries to follow.

Both France and Germany are facing elections this year, making it unclear precisely who May will be negotiating with. And the technical intricacies may take some time to unravel.

"The trading relationship is going to be the most difficult bit to solve – I don't see how that will be done in that time frame," one senior EU diplomat told Reuters.

And the exit process has complicated the situation on the home front, too. In her speech, May promised to maintain the unity of the UK’s four nations: England, Scotland, Wales, and Northern Ireland. But leaving the EU has threatened the foundations of the peace agreement in Northern Ireland, while Scotland's First Minister Nicola Sturgeon, has pledged to hold another referendum on Scottish independence in late 2018 or early 2019.

Despite these challenges, May indicated a balance can be struck. 

“While we are leaving the institutions of the European Union, we are not leaving Europe,” she said.

This report contains material from the Associated Press and Reuters.