Article 50 will finally be triggered this week, more than nine months after the historic Brexit vote. What happens now?

Brexit: everything you need to know about how the UK will leave the EU

Just over nine months after the UK’s historic vote to leave the European Union the government will this week start the formal proceedings for leaving the bloc by triggering article 50.

What is article 50?

In just 264 words in five paragraphs, article 50 of the Lisbon treaty sets out how an EU member can voluntarily leave the European Union. It specifies that a leaver should notify the European council of its intention, negotiate a deal on its withdrawal and establish legal grounds for a future relationship with the EU.

EU's chief Brexit negotiator warns of 'distinct possibility' UK will leave with no deal - Politics live Read more

Has it ever been invoked before?

No. Greenland was the last country to vote to leave the bloc, but that involved the EEC, the precursor to the EU, long before article 50 had been drafted.

What is ‘triggered’ by article 50?

Once a country gives notice it wants to leave it has two years to negotiate new arrangements, after which it will no longer be subject to EU treaties. Most of the article is fairly vague, but on this two-year timeframe the wording is unequivocal. Any extension can only be granted by unlikely unanimous agreement. The word trigger is used because invoking article 50 fires the starting gun on that two-year race to reach an agreement.

What if an agreement is not reached in two years?

The UK would still be set to leave the EU by 29 March 2019 but with no agreement there would be no provisions in place for its legal and trading relations with the bloc. Theresa May has warned that she is prepared to walk away from negotiations if she does not get what she wants. “No deal for Britain is better than a bad deal for Britain,” she said in January.

Is triggering article 50 irrevocable?

No. Lord Kerr, Britain’s former ambassador to the EU who drafted article 50, said: “It is not irrevocable. You can change your mind while the process is going on.” When the justice secretary, Liz Truss, said triggering article 50 was “irrevocable” and a “one-way ticket”, Downing Street distanced itself from the claim.

How and when will article 50 be triggered?

The Brexit starting pistol is fired on Wednesday 29 March, when the government delivers a letter to Donald Tusk, the president of the European council. At up to eight pages long, the letter is expected to be considerably longer than article 50 itself. Theresa May is expected to make a statement to MPs explaining the wording.

Then what?

On Thursday the Brexit secretary, David Davis, will publish the government’s “great repeal bill”. This will set out an end to the authority of EU law by converting all its provisions in British law once the UK leaves.

How will the EU respond?

Tusk has promised that he will respond by Friday with “draft Brexit guidelines”.

Donald Tusk (@eucopresident) Within 48 hours of the UK triggering Article 50, I will present the draft #Brexit guidelines to the EU27 Member States.

But the formal response from EU leaders is unlikely to come before a summit on 29 April, when the other EU countries meet, without the UK, to discuss guidelines for the negotiations.

When will negotiations proper begin?

Not until after the second round of the French presidential election on 7 May at the earliest, and perhaps as late as June.

How long will they take?

The EU’s chief negotiator, Michel Barnier, has said he envisages there being less than 18 months of real negotiating time. The crucial window is likely to be the year from October 2017, after the German elections on 24 September. Barnier said he hoped to begin the process of ratification by the European parliament by October 2018.

Will a deal be reached within two years?

Probably not, according to Kerr, who as well as drafting article 50 is Britain’s most experienced EU negotiator. He reckons the government has a less than 50% chance of securing an orderly exit within the timeframe and will potentially have to accept a phased departure lasting much longer, prompting “a decade of uncertainty”. Gus O’Donnell, the former cabinet secretary, also reckons it’s highly unlikely a deal can be reached in two years. Speaking before the referendum he said: “Greenland has a slightly smaller population than Croydon and it has one issue, and that’s fish. So with one issue … it took them not two years, but three. We have multiple issues. The idea that we can do it all in two years I think is highly unlikely.”

What are the key sticking points?

It’s a long list, and even the topics for negotiation are subject to negotiation. For example, the UK wants trade talks to be part of the leave discussions, but senior figures in the EU think trade should be discussed separately. While the UK is still part of the EU it is not allowed to negotiate trade deals with non-EU countries. Another key topic that will need urgent resolution will be the rights of EU citizens living in the UK and British subjects living abroad. The government ruled out giving EU citizens guaranteed protections before the start of talks, giving rise to fears that they will be used as bargaining chips. Other pressing but tricky issues include security, migration and border controls.