Video report by ITV News Political Correspondent Shehab Khan
Boris Johnson will hail the “dawn of a new era” as the UK leaves the European Union, more than three years after the referendum.
At 11pm on Friday, bonds dating back to 1973 when the UK joined the European Economic Community will be broken, but the prime minister insists Brexit marks “not an end but a beginning”.
Very little will change at the moment of Brexit as a result of the deal, which Mr Johnson agreed with Brussels and the 27 remaining member states.
But the UK faces further uncertainty as both sides seek to strike a trade deal by the end of the year.
PM visits Sunderland factory ahead of symbolic Cabinet meeting, as ITV News Political Correspondent Libby Wiener explains
It comes as the prime minister visited Sunderland to tour a design centre in the leave voting city.
As he met workers, Mr Johnson joked he was having a midlife crisis after buying a motorbike, adding: "It's the biggest joy of my life - apart from Brexit of course."
In a symbolic move, Mr Johnson then chaired a meeting of his Cabinet in Sunderland. Ministers gathered around a table to discuss the future of the country, posing for a photo opportunity.
The north-east city was the first in the country to return a vote to leave the European Union.
Downing Street said the PM and his team discussed the government's future trade agenda, which includes seeking a free trade agreement with the EU.
Controversy of PM's 'address to the nation' ahead of Brexit
In what Number 10 billed as an “address to the nation” released an hour before the moment the UK leaves the EU, Mr Johnson will attempt to sound an optimistic note about the future and promise to heal the divides which have been caused in the bitter Brexit battles.
He is expected to say: "Our job as the government – my job – is to bring this country together and take us forward."
He will call Brexit "the moment when the dawn breaks and the curtain goes up on a new act”.
"It is a moment of real national renewal and change.
"This is the dawn of a new era in which we no longer accept that your life chances – your family’s life chances – should depend on which part of the country you grow up in."
The address is to be filmed by Downing Street, rather than one of the national broadcasters in the latest clash between Number 10 and the media.
Traditionally, speeches by the PM in Number 10 have been recorded by a single broadcaster and then shared with other television networks, in what is known as a “pool” system.
UK prepares to leave EU with series of parties and memorials
On Friday afternoon, a pro-EU banner was unveiled on Westminster Bridge by campaigners mourning the UK departing from the trade bloc. Smoke flares were also set off during the protest.
The banner read: "Here to Stay. Here to Fight. Migrants In. Tories Out."
As 11pm arrives, Big Ben will remain silent, despite a high-profile campaign fuelled by Mr Johnson, for repair works to be halted to allow Parliament’s bell to ring.
But on Parliament Square, Brexiteers will gather for a party led by Nigel Farage, while Union flags are already flying around Westminster.
In official events, Downing Street will be illuminated with a light show and a new 50p coin will enter circulation.
In Brussels, the UK flag will be removed from the EU institutions, with one Union flag expected to be consigned to a museum.
Across the EU, many Britons have been left concerned about their future after Brexit. ITV News Correspondent Juliet Bremner has been speaking to British expats in Spain.
The Belgian capital has already dressed its famous Mannekin Pis statue of a urinating boy in a John Bull costume, complete with Union flag waistcoat.
In Scotland, which voted to stay in the EU in the 2016 referendum, candlelit vigils are planned.
The Leave a Light On gatherings are taking place in Aberdeen, Dundee, Glasgow, and Stirling, among other locations, and participants intend to send a message to the EU to keep open a place for Scotland.
Reaction as Brexit day arrives, three years after referendum
Politicans from across all sides of the spectrum have been reacting to the UK leaving the European Union.
Labour leader Jeremy Corbyn said: "It's a very important day for everybody, whether they voted leave or remain, because it is deciding the future direction of the country.
"We need to ensure that we maintain good relationships and we don't tear up all the agreements we've received and we don't fall into the arms of free trade deals with the United States."
He earlier stated: "We will resist a toxic Trump deal that puts our NHS, food standards and jobs at risk."
David Cameron, who led the Conservative Party and remain campaign during the referendum said: "It's obviously a very big day for our country. Obviously I led the campaign to stay in, but I always accepted the referendum result and knew this day would come.
"As I said at the time of the referendum, we're one of the biggest economies in the world; we can make a success of the choice we have made."
Meanwhile, Nicola Sturgeon, Scotland's first minister, used the day to rally supporters of Scottish independence: "So our task is to persuade a majority of people in Scotland to choose independence.
"I want to focus today on the work we need to do to persuade that majority that independence is the right and best choice, and how in the process of doing that we will secure a right to choose it in a referendum."
European leaders have expressed their sadness at the UK's departure from the EU, with European Council president Mr Michel warned that UK access to EU markets would be more restricted once it has left.
European Commission president Ursula von der Leyen echoed his thoughts, stating relations with the UK would never be as close once it is outside the EU.
"We want to have the best possible relationship with the United Kingdom but it will never be as good as membership," she said.
Washington's ambassador to the UK, Woody Johnson, welcomed the formal exit from the EU as being "long supported" by President Donald Trump.
The diplomat said the severing of the 47-year tie with the bloc will allow a transatlantic trade deal to be forged to "increase prosperity" and drive up jobs.