Updated 1.30pm with timeline

Prime Minister Theresa May will trigger Article 50 of the Lisbon Treaty, the formal notification of the United Kingdom's intention to leave the European Union, on Wednesday week, a spokesman for the British leader said today.

"Last June, the people of the UK made the historic decision to leave the EU. Next Wednesday, the government will deliver on that decision and formally start the process by triggering Article 50," Brexit minister David Davis said in a statement.

The move will begin a two-year negotiating period in which the British government and the EU hope to agree on the terms of Britain's exit and reach a separate deal on the shape of their future relationship, most importantly on the terms of trade between the two.

"We are on the threshold of the most important negotiation for this country for a generation," Davis said.

"The government is clear in its aims: a deal that works for every nation and region of the UK and indeed for all of Europe – a new, positive partnership between the UK and our friends and allies in the European Union."

EU Commission president Jean Claude Juncker is expected to be in Malta on that day and will meet Prime Minister Joseph Muscat.

The Prime Minister's letter officially notifying the European Council of the UK's intention to quit will set in train a two-year negotiation process expected to lead to Britain leaving the EU on March 29, 2019.

So what happens from now on?

• March 25 - The other 27 EU leaders meet in Rome to mark 60 years since the bloc's founding treaty. To avoid spoiling the party, May will wait till next week to file Britain's divorce notice.
• March 29 - May will write to European Council President Donald Tusk to trigger the withdrawal process.
• March 29-31 - Within 48 hours, Tusk sends to the 27 other member states his draft negotiating guidelines.
• May 4 (tentative) - Tusk needs about four weeks to prepare a summit he will chair of the 27 to agree on final guidelines and mandate the EU executive's Michel Barnier to negotiate. With Easter on April 16, the first round of French presidential voting on April 23, public holidays on May 1 and the French runoff on May 7, May 4 is a possible date.
• May 5 - Barnier will quickly reply to leaders with his detailed recommendations of how to structure talks. Holidays on May 8-9 may push him to get them to Council within a day.

DIRECTIVES

May - Ministers in the EU's normally low-key General Affairs Council will be called, again excluding Britain, to agree legal "negotiating directives" that will bind Barnier and his team.

FACE TO FACE

After nearly a year of phoney war since the June 23 referendum vote to quit, British negotiators led by Brexit Secretary David Davis will sit down with the EU, possibly still in May. Talks may start with what to discuss first and how to split up topics.

THE DIVORCE DEAL

December 2017 - Brussels wants a basic deal on a Withdrawal Treaty by year's end. Key issues: the exit bill for Britain's outstanding commitments; treatment of British and EU expats; dealing with outstanding EU legal cases; new border rules.

TRANSITION TO FUTURE RELATIONSHIP

2018 - May wants to negotiate a comprehensive free trade deal. Few see two years as enough time to agree one and Brussels wants to hold off starting talks until after a divorce deal. But London and some EU states may push for parallel trade talks.

October 2018 - Barnier's target to finalise Withdrawal Treaty, to give time for ratification by the European Parliament and a majority in the European Council by March 2019.

Autumn 2018 to Spring 2019 - Just to make things complicated, Scottish government wants independence vote once Brexit deal is clear. But May has so far rejected the call for a new Scottish referendum until after Britain leaves the EU.

B-DAY

March 30, 2019 (tentative) - Britain leaves. At any rate, it should do so two years after May writes. It happens to be a non-working day, a Saturday. And avoids April Fool's Day, April 1.

The date could be fine-tuned. Britain could leave earlier if it gets a deal, and the two-year deadline can be extended if all agree. But Brussels wants Britain out before EU elections in May 2019. Despite mutual threats of no deal, few want such chaos.

A PERIOD OF TRANSITION

May and EU leaders say transitional arrangements may well be needed, to give more time to agree a future trade deal and give people and businesses time to adjust to the divorce. Many see another two to five years after Brexit for a final settlement.

If Scotland votes for independence, expect more years to negotiate its split from London and possible re-entry to the EU.