Europe

UK set to file for EU divorce, triggering 2 years to Brexit

  • Britain's Prime Minister Theresa May signs the official letter to European Council President Donald Tusk, in 10 Downing Street, London, Tuesday March 28, 2017, invoking Article 50 of the bloc's key treaty, the formal start of exit negotiations. Britons voted in June to leave the bloc after four decades of membership. (Christopher Furlong/Pool Photo via AP)

    Britain's Prime Minister Theresa May signs the official letter to European Council President Donald Tusk, in 10 Downing Street, London, Tuesday March 28, 2017, invoking Article 50 of the bloc's key treaty, the formal start of exit negotiations. Britons voted in June to leave the bloc after four decades of membership. (Christopher Furlong/Pool Photo via AP)  (The Associated Press)

  • Britain's Prime Minister Theresa May, sitting below a painting of Britain's first Prime Minister Robert Walpole, signs the official letter to European Council President Donald Tusk, in 10 Downing Street, London, Tuesday March 28, 2017, invoking Article 50 of the bloc's key treaty, the formal start of exit negotiations. Britons voted in June to leave the bloc after four decades of membership. (Christopher Furlong/Pool Photo via AP)

    Britain's Prime Minister Theresa May, sitting below a painting of Britain's first Prime Minister Robert Walpole, signs the official letter to European Council President Donald Tusk, in 10 Downing Street, London, Tuesday March 28, 2017, invoking Article 50 of the bloc's key treaty, the formal start of exit negotiations. Britons voted in June to leave the bloc after four decades of membership. (Christopher Furlong/Pool Photo via AP)  (The Associated Press)

  • Britain's Prime Minister Theresa May signs the official letter to European Council President Donald Tusk, in 10 Downing Street, London, Tuesday March 28, 2017, invoking Article 50 of the bloc's key treaty, the formal start of exit negotiations. Britons voted in June to leave the bloc after four decades of membership. (Christopher Furlong/Pool via AP)

    Britain's Prime Minister Theresa May signs the official letter to European Council President Donald Tusk, in 10 Downing Street, London, Tuesday March 28, 2017, invoking Article 50 of the bloc's key treaty, the formal start of exit negotiations. Britons voted in June to leave the bloc after four decades of membership. (Christopher Furlong/Pool via AP)  (The Associated Press)

Britain is set to formally file for divorce from the European Union, ending a 44-year relationship following the decision made by U.K. voters in a referendum nine months ago.

Prime Minister Theresa May is due to tell House of Commons Wednesday afternoon that she has invoked Article 50 of the EU's key treaty, the trigger for a two-year countdown to Britain's exit.

At the same time, Britain's EU envoy, Tim Barrow, will hand-deliver a letter from May, which she signed Tuesday at her 10 Downing St. office, to EU Council President Donald Tusk.

May's office says she will tell lawmakers that the U.K. is embarking on a "momentous journey" and should unite to forge a "global Britain."

Britain and the EU have two years to unpick a tapestry of rules, regulations and agreements stitched over more than four decades since Britain joined what was then the European Economic Community in 1973.

EU officials are due to circulate draft negotiating guidelines within days, and bloc leaders — minus May — will meet April 29 to adopt a common position.

Britain says it's not turning its back on its neighbors and wants to remain friends. May has said that the U.K. will become "stronger, fairer, more united and more outward-looking" and will seek "a new, deep and special partnership with the European Union."

But many British businesses fear the impact of leaving the EU's vast single market of some 500 million people. Senior British officials say they are confident of striking a close new free-trade relationship with the bloc — but a successful outcome to the complex and emotionally fraught negotiations is far from certain.

Brexit has profound implications for Britain's economy, society and even unity. The divisive decision to leave the EU has given new impetus to the drive for Scottish independence, and undermined the foundations of Northern Ireland's peace settlement.

It's also a major blow to the EU, after decades of expansion, to lose one of its largest members. Anti-EU populists including French far-right leader Marine Le Pen hope the impulses that drove Britain to turn its back on the EU will be repeated across the continent.