U.K. Prime Minister makes Brexit official

U.K. Prime Minister Theresa May invoked Article 50 of the Lisbon Treaty in a six-page letter, which was handed over in Brussels.

Speaking to MPs in the House of Commons, the Prime Minister described it as a “historic moment from which there can be no turning back” when the letter was handed from the British ambassador, Sir Tim Barrow, to E.U. council president Donald Tusk. Tusk was described as “visibly upset,” and urged people not to “pretend it is a happy day.”

Article 50 allows for a two-year period of negotiations over the terms of withdrawal, putting the United Kingdom on track to formally leave the European Union on March 29, 2019. The negotiations will involve everything from deals on trade, migration, education and healthcare.

In the House of Commons, May promised to represent all of the United Kingdom in the negotiations to come.

The United Kingdom is the first country to trigger Article 50 to exit the European Union.