The countdown is on until the UK leaves the European Union, bringing an end to 47 years of membership.
Across the nation there is a mixture of celebration and regret that at 11pm, almost four years on from the 2016 referendum, Britain will cease to be a member.
Prime Minister Boris Johnson called it an “astonishing moment of hope” in a video message to mark Brexit day, while Downing Street will be illuminated with a light show.
The PM is also hosting a reception in Number 10 for cabinet ministers, advisers and civil servants, officials who were involved in the negotiations, and supporters of the Leave campaign.
Backers and opponents of Brexit have been making their views known throughout Britain, with Westminster a particular focus for events.
Hundreds of Brexit supporters have gathered for a party led by Nigel Farage on Parliament Square.
A sound system was set up on the back of a lorry, with people dancing to music by Sir Tom Jones and Queen.
Dozens gathered around the statue of Sir Winston Churchill, with some ringing bells and banging a drum attached to a modified cart dubbed Little Ben.
Earlier, pro-EU demonstrators took part in a procession through Whitehall.
A crowd also gathered across the road from Number 10, brandishing EU flags and anti-Brexit placards.
The message “we still love EU” was beamed onto the White Cliffs of Dover.
It comes after a love letter to the bloc from two Second World War veterans was projected onto the cliffs.
The video ends with the stars of the EU flag slowly disappearing, leaving just one star left.
“This is our star. Look after it for us,” the last message says.
Candlelit vigils are taking place in Scotland, which voted to stay in the EU.
Leave a Light On gatherings will take place in Aberdeen, Dundee, Glasgow, and Stirling, among other locations.
Participants want to send a message to the EU to keep open a place for Scotland, amid a renewed bid from the SNP for a second independence referendum.
In Northern Ireland, there will be a series of protests in Armagh, close to the border with the Republic of Ireland.
In Brussels, the EU has been preparing for life without Britain in the bloc.
The British flag has been removed from its flagpole outside the European Parliament and will be placed in a museum.