So long, farewell, auf wiedersehen, adieu.

With little fuss and not much fanfare, Britain has left the European Union after 47 years of membership, taking a leap into the unknown in a historic blow to the bloc.

Peter Morrison/AP Brexit supporters celebrate during a rally outside Stormont in Belfast, Northern Ireland.

The UK's departure became official at 11 pm (UK time), midnight in Brussels, where the EU is headquartered.

Thousands of enthusiastic Brexit supporters gathered outside Britain's Parliament cheered as the hour struck.

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They had been hoping for this moment since Britain's 52 to 48 per cent vote in June 2016 to walk away from the club it had joined in 1973.

UK Prime Minister Boris Johnson called Britain's departure "a moment of real national renewal and change."

Kirsty Wigglesworth/AP A countdown to Brexit timer and the colors of the British Union flag illuminate the exterior of 10 Downing street, the residence of the British Prime Minister.

But many Britons mourned the loss of their EU identity, and some marked the passing with tearful vigils.

There was also sadness in Brussels as British flags were quietly removed from the bloc's many buildings.

Francois Mori/AP British living in France attend a gathering to express their spirit of Europe despite the withdrawal Brexit agreement and the UK's departure from the EU, in a pub close to the British Embassy in Paris.

Whether Brexit makes Britain a proud nation that has reclaimed its sovereignty, or a diminished presence in Europe and the world, will be debated for years to come.

While Britain's exit is a historic moment, it only marks the end of the first stage of the Brexit saga. When Britons wake up in the morning, they will notice very little change.

Anthony Devlin/Getty Guests celebrate the moment the UK leaves the EU during the Brexit party at Woolston Social Club.

The UK and the EU have given themselves an 11-month "transition period" - in which the UK will continue to follow the bloc's rules - to strike new agreements on trade, security and a host of other areas.

The now 27-member EU will have to bounce back from one of its biggest setbacks in its 62-year history to confront an ever more complicated world as its former member becomes a competitor, just across the English Channel.

Alberto Pezzali/AP Brexit supporters celebrate during a rally in Parliament square in London as Britain leaves the European Union.

French President Emmanuel Macron called Brexit a "historic alarm signal" that should force the EU to improve itself.

"It's a sad day, let's not hide it," he said in a televised address. "But it is a day that must also lead us to do things differently."

He insisted that European citizens need a united Europe "more than ever," to defend their interests in the face of China and the United States, to cope with climate change and migration and technological upheaval.

AP The office of British European Parliament member Nigel Farage at the European Parliament in Brussels earlier this week. UK parliamentarians packed boxes and removed personal items from their EU offices.

In the many EU buildings of Brussels on Friday, British flags were quietly lowered, folded and taken away. This is the first time a country has left the EU, and many in the bloc rued the day.

EU Commission President Ursula von der Leyen lamented that "as the sun rises tomorrow a new chapter for our union of 27 will start."

But she warned Brexit day would mark a major loss for the UK and said the island nation was heading for a lonelier existence.

"Strength does not lie in splendid isolation, but in our unique union," she said.

Leon Neal/Getty Pro Brexit supporters celebrates as the United Kingdom exits the EU during the Brexit Day Celebration Party hosted by Leave Means Leave at Parliament Square.

UK Prime Minister Boris Johnson insisted post-Brexit Britain would be "simultaneously a great European power and truly global in our range and ambitions."

"We want this to be the beginning of a new era of friendly cooperation between the EU and an energetic Britain," Johnson said in a pre-recorded address to the country broadcast an hour before Britain's exit.

In a break with usual practice, independent media outlets were not allowed to film Johnson's speech, which the government recorded the day before at 10 Downing St.

Frank Augstein/AP A Brexit supporter dances during a rally in London.

Johnson won an election victory in December with a dual promise to "get Brexit done" and deliver improved jobs, infrastructure and services for Britain's most deprived areas, where support for leaving the EU is strongest.

On Friday (Saturday New Zealand time), he symbolically held a Cabinet meeting in the pro-Brexit town of Sunderland in northeast England, rather than in London.

Johnson is a Brexit enthusiast, but he knows many Britons aren't, and his Conservative government aimed to mark the moment with quiet dignity.

Red, white and blue lights illuminated government buildings and a countdown clock projected onto the prime minister's Downing Street residence.

Alberto Pezzali/AP A Brexit supporter celebrates during a rally in Parliament square in London.

There was no such restraint in nearby Parliament Square, where arch-Brexiteer Nigel Farage gathered a crowd of several thousand, who belted out the patriotic song Land of Hope and Glory as they awaited a moment that even Farage sometimes doubted would ever come.

Londoner Donna Jones said she had come to "be part of history."

"It doesn't mean we're anti-Europe, it just means we want to be self-sufficient in a certain way," she said.

Frank Augstein/AP Brexit Party leader Nigel Farage effectively campaigned his job as a Member of the European Parliament out of existence.

But Britons who cherished their membership in the bloc - and the freedom it bought to live anywhere across of 28 countries - were mourning.

"Many of us want to just mark our sadness in public," said Ann Jones, who joined dozens of other remainers on a march to the EU's mission in London.

"And we don't want trouble, we just want to say, well you know, we didn't want this."

Kirsty Wigglesworth/AP Britain has left the European Union.

Britain's journey to Brexit has been long, rocky - and far from over.

The UK was never a wholehearted EU member, but actually leaving the bloc was long considered a fringe idea.

It gradually gained strength within the Conservative Party, which has a wing of fierce "euroskeptics" - opponents of EU membership. Former Prime Minister David Cameron eventually agreed to hold a referendum, saying he wanted to settle the issue once and for all.

It hasn't worked out that way. Since the 2016 vote, the UK has held fractious negotiations with the EU that finally, late last year, secured a deal on divorce terms. But Britain is leaving the bloc arguably as divided as it was on referendum day.

Kirsty Wigglesworth/AP Britain's Foreign Office lit up for the Brexit night, in London.

By and large, Britain's big cities voted to stay in the EU, while small towns voted to leave. England and Wales backed Brexit, while Northern Ireland and Scotland voted to remain.

Candlelit vigils were held in several Scottish cities, government buildings in Edinburgh were lit up in the EU's blue and yellow colours, and the bloc's flag continued to fly outside the Scottish Parliament.

Frank Augstein/AP Brexit supporters trample on a European Union flag during a rally in London.

Scottish First Minister Nicola Sturgeon said Brexit "will be a moment of profound sadness for many of us across the UK"

"And here in Scotland, given that it is happening against the will of the vast majority of us, that sadness will be tinged with anger," she said in a speech in Edinburgh.

Tim P. Whitby/Getty Images for Sky UK Brexit day marked with a farewell message on the white cliffs of Dover.

Sturgeon's Scottish National Party government is demanding the right to hold a referendum on independence from the UK, something Johnson refuses to grant.

London, which is home to more than 1 million EU citizens, also voted by a wide margin to stay in the bloc.

Mayor Sadiq Khan said he was "heartbroken" about Brexit. But he insisted London would remain that welcomed all, regardless of "the colour of your skin, the colour of your flag, the colour of your passport."

Tim P. Whitby/Getty Images for Sky UK Brexit day is marked with a farewell message on the white cliffs of Dover.

Negotiations between Britain and the EU on their new relationship are due to start in earnest in March, and the early signs are not encouraging.

The EU says Britain can't have full access to the EU's single market unless it follows the bloc's rules, but Britain insists it will not agree to follow an EU rulebook in return for unfettered trade.

With Johnson adamant he won't extend the transition period beyond December 31, months of uncertainty and acrimony lie ahead.

Alberto Pezzali/AP A dog wearing a Union Jack outfit is held for a photograph near the gates of Downing street, in London.

In the English port of Dover, just 32 kilometres across the Channel from France, retiree Philip Barry said he was confident it would all be worth it.

"My expectation is that there may be a little bump or two in the road but in the end it will even out," he said. "Somebody once said: short-term pain but long- term gain."

Associated Press video journalists Jo Kearney and Philipp-Moritz Jen ne contributed. Casert reported from Brussels.