Theresa May will urge Britons to come together when she triggers Article 50 today.

In a statement to MPs, the Prime Minister will say now is the time for national unity to achieve the best possible Brexit deal.

She will say we should be ‘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,’ she will add.

‘Now that the decision has been made to leave the EU, it is time to come together.’

Sat in the cabinet office of Downing Street, May last night signed her name under the watchful eye of Sir Robert Walpole, the country's first ever Prime Minister.

Theresa May officially invokes Article 50 as she signs a letter to EU Council President Donald Tusk, under the watchful eye of Britain's first Prime Minister Robert Walpole (pictured)

Mrs May is pictured in the Cabinet Office signing the letter - which is rumoured to run to eight pages - before it is couriered to the EU’s capital

The landmark document (pictured) will be handed over by Britain's EU ambassador Sir Tim Barrow and represents the first act of an irreversible Brexit process

It emerged last night that Britain will obey Brussels free movement rules for up to two more years.

Ministers had considered using the official notification as a ‘cut-off point’, denying new EU arrivals the automatic right to stay here. But sources last night confirmed that this idea had been dropped and the timing of the cut-off will form part of the Brexit negotiations.

The decision on free movement last night raised fears of a rush by EU migrants to beat the deadline.

A government source insisted the Prime Minister had not avoided an early confrontation with Brussels in order to ease the opening of negotiations.

‘We have not ducked anything,’ the source said. ‘The fact is that we have not got a reciprocal deal on the rights of citizens abroad so we cannot set a date for the start of a new system.’

Another source said the Home Office was concerned about the practical difficulties of enforcing a cut-off date before the introduction of a new post-Brexit immigration regime.

The Prime Minister will write a letter that will be delivered by hand to EU Council President Donald Tusk, pictured marking the EU's 60th anniversary on Saturday, at around 12.30pm

The letter was due to be conveyed to Brussels by diplomats tonight to be handed to Mr Tusk by Britain’s ambassador to the EU Sir Tim Barrow at lunchtime today

Mrs May last night signed the letter to European Council president Donald Tusk informing him that the UK is triggering Article 50 of the Lisbon Treaty, the formal method of leaving the 28-member bloc.

The letter was due to be conveyed to Brussels by diplomats last night to be handed to Mr Tusk by our ambassador to the EU Sir Tim Barrow at lunchtime today. It starts a two-year process that will see the UK leave on March 29, 2019.

ARTICLE 50: WHAT HAPPENS NEXT Theresa May's letter to Donald Tusk invoking Article 50 will be handed over at around 12.30pm. This is the point of no return and will trigger two years of frantic diplomacy and negotiations. Within 48 hours, the EU will issue its first response and the 27 remaining members are set to meet in late April. The first major summit is likely to be later in the spring - but talks could be limited by pending elections in Germany. The final deal is expected to emerge by the end of next year in time for a series of votes on ratification Brussels, London and around Europe. If the talks collapse at any point in the two years, Britain could face leaving the EU without a deal at all. Advertisement

The Prime Minister will pledge to represent ‘every person in the UK’, during talks with Brussels, including diehard Remain voters and 3.2million EU citizens living here. Setting out her ambitions for the negotiations, she will pledge to make the UK stronger, fairer and more secure.

‘It is my fierce determination to get the right deal for every single person in this country,’ she will 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.’

Sources last night said the letter to Mr Tusk would set out the broad principles of Mrs May’s negotiating aims, without getting into the detail.

The document is expected to confirm that Brexit will involve the UK’s departure from the EU’s single market, because membership would mean accepting free movement and EU court rulings.

Mrs May is expected to demand that trade talks are conducted in parallel with wrangling over the terms of the UK’s exit. EU leaders have warned of a £50billion divorce bill.

The Prime Minister will call for an early agreement guaranteeing the rights of 3.2million EU citizens living in the UK and 1.2million British citizens in Europe.

Government lawyers have warned that any cut-off prior to the end of Britain’s EU membership would inevitably face court challenges.

Sources last night said a date was unlikely to be set until a deal on reciprocal citizen rights has been agreed.

Brexit Secretary David Davis and Home Secretary Amber Rudd were both seen arriving in Downing Street tonight as the finishing touches were put to the Article 50 letter

IN FULL: MAY'S WARCRY TO THE UK AHEAD OF BREXIT 'When I sit around the negotiating table in the months ahead, I will 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. '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. '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.' Advertisement

The European Parliament yesterday threatened to block a final Brexit deal if the UK tried to introduce a cut-off before its full departure from the EU.

A resolution setting out MEPs’ demands will be voted on next week and will include a provision for ‘non-discrimination’ against EU citizens in the UK.

A source who has seen the document said: ‘The Parliament will demand that EU free movement law is applied until the day the UK leaves.’

The Article 50 process has never been used before. Ministers believe that, after today, the UK’s departure from the organisation it joined in 1973 will be irrevocable.

Mr Tusk will set out the EU’s ‘draft negotiation guidelines’ by the end of the week before sending them to the 27 remaining states for consultation.

EU leaders will meet on April 29 at an extraordinary European Council summit to agree a mandate for chief negotiator Michel Barnier and clear the way for talks to begin in earnest in May.

'Gloomy' Brexit report sparks MPs' walkout

Tory MPs staged an unprecedented walkout from a cross-party committee on Brexit yesterday in protest against a ‘massively skewed’ report.

During a stormy meeting at Westminster, pro-Brexit MPs complained that the committee’s Labour chairman Hilary Benn had failed to consult them before presenting them with a 155-page report savaging the Government’s handling of Britain’s departure from the EU.

A source said Mr Benn, a former Cabinet minister, tried to pressure committee members into signing the ‘gloomy’ report.

When Mr Benn refused to back down, three Tories walked out – Dominic Raab, Maria Caulfield and Karl McCartney.

A source said Hilary Benn (pictured) tried to pressure committee members into signing the ‘gloomy’ report

The other six pro-Brexit members of the 21-strong committee are also expected to vote against the report’s findings, rendering it almost worthless. Last night they were even discussing the release of a minority report setting out a more balanced appraisal of the Government’s approach to Brexit.

One source on the panel accused Mr Benn of ‘trying to use the committee to fire an Exocet [missile] at the Government in the week it triggers Article 50’.

The source added: ‘Normally when you are drawing up a committee report you start with a debate about the principles.

‘This time, we were presented with a 155-page draft report that is massively skewed against Brexit. We were told we could offer some drafting suggestions, but there is no point doing that when the report itself is irredeemably flawed.

‘Several of us suggested that we go back to first principles, but when this idea was rejected, there didn’t seem much point in staying. It was perfectly amicable but pretty frustrating.’

'BRUSSELS OWES UK A TRILLION EUROS' The UK should sidestep demands for a hefty ‘divorce bill’ during Brexit talks by handing Brussels a one-trillion Euro counter claim. The audacious approach in a report by a leading think-tank called for Downing Street to demand compensation for inefficiency and bad practice since the UK joined the EU. Disputes over the £52billion ‘divorce bill’, which covers contributions towards eurocrat pensions and future EU budgets, is likely to prove contentious. Leading EU figures yesterday refused to back down and said they would only approve a Brexit deal that was ‘very costly’ for the UK. But the Civitas think-tank’s report calls for the UK to launch a significant array of financial claims during negotiations. The cross-party body said that the UK should enter compensation claims for ‘fraudulent and extravagant’ EU use of British funds, as well as increased military expenditure caused by EU recklessness. It calls for a £22billion compensation claim for being associated with the ‘EU’s chronic dysfunction and maladministration’, as well as £48billion in financial damage caused by European banks. Advertisement

Former Tory Cabinet minister Peter Lilley, who is on the committee, was not at yesterday’s meeting but said he was ‘not happy’ with Mr Benn’s report.

A spokesman for the committee said Mr Benn would not be commenting on the row, adding: ‘We do not comment on private discussions.’ But the failure to reach a consensus means the committee’s report on the Government’s Brexit white paper now risks being fatally undermined when it is published later this week.

It also highlights concerns about the operation of the committee, which has an in-built majority of Remain MPs including Mr Benn, who played a prominent role in the campaign to keep Britain in the EU last year.

The committee, which is almost twice the size of a normal Commons committee, is made up of 12 pro-Remain MPs and just nine who supported Brexit.

Eurosceptic Tory MP Peter Bone said yesterday’s walkout raised question marks about the future operation of the committee.

‘It is unheard of for MPs to walk out of a private meeting during deliberations on a report,’ he said.

‘It does appear that the chairman is trying to use the committee to promote a personal, pro-Remain agenda, which does not reflect the mood in the country. I am not sure this committee can work if it carries on like this. The whole point about select committees is to reach a consensus. Unless you can do that, any conclusions you reach are pretty pointless.’

But pro-Remain MPs yesterday insisted the committee was working.

Alistair Burt, a former Tory Foreign Office minister who is on the panel, dismissed the walkout, posting a message on Twitter saying: ‘Rest of Committee still sitting and doing its job to consider the report.’

Anna Soubry, one of the most Europhile Tory MPs, said the committee was fully entitled to produce a ‘gloomy’ report on Brexit, adding: ‘Gloomy = Brexit reality. It doesn’t have to be like this. Membership of the single market will make our prospects brighter.’

Committee sources said the report is likely to be published this week.