British Prime Minister Theresa May has formally begun the process of the UK leaving the European Union, by sending a letter of intent to European Council President Donald Tusk, triggering Article 50 of the Treaty of Lisbon and paving the way for the biggest political upheaval in the EU’s history.

Nine months after Britain voted to leave the EU in a referendum, June 23, 2016, May has fired the starting pistol on the negotiations on Britain leaving the EU and finding a new relationship with the remaining 27 members post-Brexit.

​In her letter to Tusk, May wrote: “The United Kingdom wants to agree with the European Union a deep and special partnership that takes in both economic and security cooperation. To achieve this, we believe it is necessary to agree the terms of our future partnership alongside those of our withdrawal from the EU.

“We want to be able to agree a deep and special partnership, taking in both economic and security cooperation, but it is also because we want to play our part in making sure that Europe remains strong and prosperous and able to lead in the world, projecting its values and defending itself from security threats. And we want the United Kingdom to play its full part in realizing that vision for our continent,” she wrote.

It is the first time that Article 50 has been invoked and it was — ironically — drafted by British Diplomat Lord Kerr of Kinlochard, who has said he did not have Brexit in mind when writing the clauses. It was intended as a safety mechanism in the event of a coup in one of the member states.

Theresa May telephoned Tusk, German Chancellor Angela Merkel and EU Commission President Jean-Claude Juncker on the evening of March 28, saying that a “strong EU was in everyone’s interests and that the UK would remain a close and committed ally,” according to Downing Street sources.

They also agreed on the importance of entering into negotiations in a constructive and positive spirit, and of ensuring a smooth and orderly exit process.

“This is an historic moment from which there can be no turning back. Britain is leaving the EU. We are going to make our own decisions, and our own laws. We are going to take control of the things that matter most to us,” May told the House of Commons, May 29.

“At moments like these — great turning points in our national story — the choices we make define the character of our nation. We can choose to say the task ahead is too great. We can choose to turn our face to the past an believe it can’t be done. Or we can look forward with optimism and hope and to believe in the enduring power of the British spirit. I choose to believe in Britain and that our best days lie ahead,” she told parliament.