A total of 277 days after the UK voted to leave the EU, the Prime Minister will trigger Article 50 of the Lisbon Treaty, starting the clock on a two-year formal negotiation process that will see Brexit take place by 28 March, 2019.
In an appeal to national unity, Mrs May will say the people of the UK are “no longer defined by the votes we cast” in the referendum last year, and should work together to help build a “global Britain” that is stronger and fairer outside the EU.
And highlighting her refusal to consider a second referendum on Scottish independence until after the Brexit process is concluded, she will insist the UK is “one great union of people and nations with a proud history and a bright future”.
Last night the Prime Minister put her signature to a letter that will be hand-delivered to the president of the European Council, Donald Tusk, at 12:30pm this afternoon.
She spoke by telephone to German Chancellor Angela Merkel, Mr Tusk and EU Commission president Jean-Claude Juncker, agreeing that both sides should go into negotiations “in a constructive and positive spirit”, a Downing Street spokeswoman said.
The contents of the letter, which is expected to set out as-yet unseen detail about the government’s objectives for Brexit talks, is commercially sensitive and will only be published online once she has finished her statement.
After Prime Minister’s Questions today, Mrs May will tell MPs that she is going into the upcoming negotiations to “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. And yes, those EU nationals who have made this country their home.
“It is my fierce determination to get the right deal for every single person in this country,” she is expected to say.
“For, as we face the opportunities ahead of us on this momentous journey, our shared values, interests and ambitions can – and must – bring us together.
“We all want to see a Britain that is stronger than it is today. We all want a country that is fairer so that everyone has the chance to succeed.
“We all want a nation that is safe and secure for our children and grandchildren. We all want to live in a truly global Britain that gets out and builds relationships with old friends and new allies around the world.
The Prime Minister will add: “These are the ambitions of this government’s plan for Britain. Ambitions that unite us, so that we are no longer defined by the vote we cast, but by our determination to make a success of the result.
“We are one great union of people and nations with a proud history and a bright future. And, now that the decision has been made to leave the EU, it is time to come together.”
Negotiations are not expected to begin in earnest until after German elections in September. However, Mr Tusk has said an initial formal response to the Prime Minister’s letter will be ready within 48 hours.
EU leaders will then meet at a summit on 29 April to discuss their approach to negotiations.
Yesterday Michel Barnier, the man appointed by the European Commission to lead negotiations for the EU, underlined his priority of securing the rights of EU nationals living in the UK.
He met campaigners representing three million EU citizens, and tweeted: “Brexit made EU citizens worry about their future in EU27 and UK. EU will be firm on their rights”.
However, it is understood that Mr Barnier will insist on the conclusion of a “divorce” settlement of up to £50 billion before anything else is discussed.
Brexit Secretary David Davis reiterated the government’s refusal to accept a bill approaching that figure. “I don’t think we are going to be seeing that sort of money change hands,” he said.
Jeremy Corbyn said pressure was on Mrs May to return from Brussels with a Brexit deal that preserves current EU social protections.
“The Conservatives want to use Brexit to turn our country into a low-wage tax haven,” the Labour leader said. “Labour is determined to ensure we can rebuild and transform Britain, so no-one and no community is left behind.
“It will be a national failure of historic proportions if the Prime Minister comes back from Brussels without having secured protection for jobs and living standards.”
Liberal Democrat leader Tim Farron, whose party is committed to holding a second referendum on EU membership and taking the UK back into the bloc, said it was not too late for the country to change its mind.