EU President Donald Tusk received on Wednesday a notification letter from the British ambassador to the Union that triggers a two-year countdown to Brexit under Article 50 of the EU treaty.

Britain formally launched the process to leave the EU on Wednesday with Ambassador Tim Barrow personally delivering the letter, signed by British Prime Minister Theresa May, at Tusk’s office in Brussels, the journalist said.

“After nine months the UK has delivered. #Brexit,” Tusk tweeted after he received the letter, referring to Britain’s shock June 23, 2016 referendum vote to leave the EU.

May signed the letter in Downing Street on Tuesday, a photo released by her office showed.

Just days after the EU’s 60th birthday, Britain will become the first country ever to seek a divorce, striking a blow at the heart of the union forged from the ashes of World War II.

Now is the time for Britain to come together and ensure it gets the best Brexit deal possible, May said on Wednesday after the country formally triggered its exit from the European Union.

“Now is the time for us to come together and be united across this house (of parliament) and across this country to ensure that we work for the best possible deal for the United Kingdom and the best possible future for us all,” May told parliament.

She said Britain would seek to agree its future partnership with the bloc alongside the withdrawal terms, adding that she knows there will be consequences with leaving the EU.

Meanwhile, a spokesman for the German Foreign Ministry said that the two-year timetable for Britain and the EU to settle the terms of their split is very tight.

“The time-frame is damn narrow,” Martin Schaefer said at a regular government news conference.