Prime Minister Theresa May filed formal Brexit divorce papers on Wednesday, pitching the United Kingdom into the unknown and triggering years of uncertain negotiations that will test the endurance of the European Union.
Nine months after Britons voted to leave, May notified EU Council President Donald Tusk in a letter that the UK is quitting the bloc it joined in 1973.
The prime minister, an initial opponent of Brexit who won the top job in the political turmoil that followed the referendum vote, now has two years to settle the terms of the divorce before it comes into effect in late March 2019.
"Now that the decision has been made to leave the EU, it is time to come together," May said in a statement issued by her office.
"When I sit around the negotiating table in the months ahead, I will represent every person in the whole United Kingdom – young and old, rich and poor, city, town, country and all the villages and hamlets in between," she said.
On the eve of Brexit, May, 60, has one of the toughest jobs of any recent British prime minister: holding Britain together in the face of renewed Scottish independence demands, while conducting arduous talks with 27 other EU states on finance, trade, security and other complex issues.
The outcome of the negotiations will shape the future of Britain's $2.6 trillion economy, the world's fifth biggest, and determine whether London can keep its place as one of the top two global financial centres.
For the EU, already reeling from successive crises over debt and refugees, the loss of Britain is the biggest blow yet to 60 years of efforts to forge European unity in the wake of two devastating world wars.
Its leaders say they do not want to punish Britain. But with nationalist, anti-EU parties on the rise across Europe, they cannot afford to give London generous terms that might encourage other member states to break away.
May's notice of the UK's intention to leave the bloc under Article 50 of the EU's Lisbon Treaty was hand-delivered to Tusk in Brussels by Tim Barrow, Britain's permanent representative to the EU.
Barrow handed the letter to Tusk, the EU summit chair and former Polish prime minister, in the Council President's offices on the top 11th floor of the new Europa Building.
May signed the Brexit letter on Tuesday, pictured alone at the cabinet table beneath a clock, a British flag and an oil-painting of Britain's first prime minister, Robert Walpole.
United Kingdom? At home, May's United Kingdom - a nuclear power with a permanent seat on the United Nations Security Council - is divided and faces strains that could lead to its break-up. The results of the Brexit referendum called the country's future into question because England and Wales voted to leave the EU but Scotland and Northern Ireland voted to stay. Scottish nationalists have demanded an independence referendum that May has refused, saying the time is not right. In Northern Ireland, rival parties have been unable to end a major political crisis for over two months and Sinn Fein nationalists are demanding a vote on leaving the UK and uniting with the Republic of Ireland. "May's job is just so difficult - keeping the UK together while Brexiting - that I am not sure anyone would want it," said a senior non-EU diplomat, who spoke on condition of anonymity. "After Brexit, the future of almost everything is completely unclear and that is extremely worrying for the UK, the EU and the West as a whole."
After nine months the UK has delivered. #Brexit— Donald Tusk (@eucopresident) March 29, 2017
Today, the formal process for Brexit begins. Here’s what you need to know pic.twitter.com/5rgv4rtbMx — The Economist (@TheEconomist) March 29, 2017