Prime Minister Theresa May on Wednesday, March 29 signed the Article 50 letter, as she prepares to trigger the start of the UK's formal withdrawal from the EU, Belfast Telegraph reports.

Signed personally by May, the exit letter will be delivered to European Council president Donald Tusk.

The triggering of Article 50 of the Lisbon Treaty, which governs EU law, will open a two-year window for Britain to negotiate the terms of its exit from the bloc, unraveling 44 years of ties. U.K. government officials say there is no going back from there.

"It is my fierce determination to get the right deal for every single person in this country," Prime Minister Theresa May will say in a speech to Parliament after the letter is delivered, according to excerpts from her office.

The negotiations are expected to be tough and test the unity of the bloc. Early indications are that Britain and the EU are far apart. May has said Britain won't abide by the bloc's court or immigration rules once it leaves, but that it wants to continue to trade as freely as possible with the EU. European leaders say they don't want to punish the U.K., but won't grant Britain a better deal outside the club than it has in it.