Prime Minister Boris Johnson will hail the “dawn of a new era” on Friday, as the UK prepares to leave the European Union after 47 years.
In a speech to be shown at 22:00 GMT – an hour before the official departure time – he will say Brexit is “not an end but a beginning”.
He will describe severing ties with the other 27 EU nations as “a moment of real national renewal and change”.
Little will change immediately, as the UK begins a “transition period”.
Most EU laws will continue to be in force – including the free movement of people – until the end of December, by which time the UK aims to have reached a permanent free trade agreement with the EU.
In a statement, Labour leader Jeremy Corbyn urged the country not to “turn inwards” and instead “build a truly internationalist, diverse and outward-looking Britain’”.
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Brexit was originally scheduled for 31 March last year but was repeatedly delayed when MPs rejected a previous withdrawal agreement reached by the EU and former Prime Minister Theresa May.
Mr Johnson was able to get his own deal through Parliament after winning December’s general election with a House of Commons majority of 78, on a pledge to “get Brexit done”.
This brought to an end more than three years of political wrangling, following the referendum of 2016, in which 52% of voters backed leaving the EU.
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To mark Brexit, Mr Johnson will hold a cabinet meeting in Sunderland – the city that was the first to back Brexit when results were announced after the 2016 referendum – on Friday morning.
The prime minister – who led the 2016 campaign to get the UK out of the EU – will attempt to strike an optimistic, non-triumphalist note in his speech, stressing the need to bring all side together.
“The most important thing to say tonight is that this is not an end but a beginning,” he will say.
“This is 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.”
Image copyright Getty Images Image caption Tourists pose for pictures with Mannekin Pis statue in Brussels
In his address, filmed in Downing Street, Mr Johnson will also say: “This is the dawn of a new era in which we no longer accept that your life chances –