Britain leaves the European Union today and starts work to rewrite its relationship with the bloc. Britain joined what was then called the European Economic Community on January 1, 1973, and voted out on June 23, 2016 in a referendum by the Tories.
Brexit is the United Kingdom's biggest geopolitical move in decades.
What will change and what will stay the same when Britain officially leaves the European Union on Friday at 2300 GMT?
While the United Kingdom remains a member in all but name, it loses its vote in the meetings in Brussels that ultimately decide EU policy on matters ranging from financial services to the definition of a European-made car.
The United Kingdom accounts for about 15 per cent of the EU's economy and is its biggest military spender, and the City of London is the world’s international financial capital.
But the United Kingdom's economy is worth about $2.7 trillion economy, so is much smaller than the EU's current $18.3 trillion economy.
Brussels will try to discern exactly how Prime Minister Boris Johnson plans to overhaul the United Kingdom: will he try to build a competitor just outside the EU by turbo-charging the economy and the City of London?
British and EU citizens will continue to have the right to live and work in each other's countries until the end of the year because both sides agreed a transition period which preserves membership in all but name until 2021.
The British government has told the estimated 3.5 million EU citizens living in Britain that they have until at least the end of the December to register to retain their rights.
Johnson has said he will introduce an Australian points-based immigration system after Brexit which he says would allow talented people into the country while barring entry to low-skilled workers.
Companies and customs
The regulatory environment for companies won’t change following Brexit because of the transition period.
After the end of the transition deal, UK customs will apply for goods coming from third countries to Northern Ireland only. For goods deemed to be headed for the EU market, UK authorities will collect EU tariffs.
There will be no customs checks on the island of Ireland – they will be done in ports. UK authorities will be in charge of applying the EU customs rules in Northern Ireland.
As soon as the United Kingdom formally leaves the EU on January 31, it can start negotiating trade deals with other countries.
The European Union –– which accounts for about half of the United Kingdom's trade –– and the US are the government's top targets for securing new trade deals.
A sticking point in US talks will be a British proposal for a unilateral digital services tax, despite a US threat to levy retaliatory tariffs on British-made autos.
There will in effect be no change for Britain’s vast financial services industry dealing with customers in the EU for the next 11 months because of the transition period.
All EU financial rules will still be applicable in Britain until the end of December. Banks, asset managers and insurers in Britain will continue to have full, unfettered access to investors in the bloc during that period.
The sector's future access to investors in the EU will be one of the first issues to be discussed and must be finalised by the end of June.
The government will be looking for the EU to make what is known as an "equivalence" ruling to allow those firms to continue trading with the bloc.
Chief characters in Britain's Brexit saga
Here are some of the public figures who have played pivotal roles in events.
A eurosceptic member of the European Parliament and former leader of the UK Independence Party (UKIP), Farage has campaigned to leave the EU for 25 years.
It was a surge in support for UKIP in the first half of the last decade that helped push Cameron into calling the 2016 vote.
By focussing his campaign on mass immigration, Farage attracted a great deal of controversy.
Following the surprise victory by the "Leave" side, he initially said he would withdraw from frontline politics, but returned in 2019 denouncing what he saw as a "betrayal" of Brexit under then-premier Theresa May.
Farage founded the Brexit Party and stormed into first place in European Parliament elections in May last year.
But after Johnson replaced Theresa May as Prime Minister, Farage found his new party marginalised and it failed to win any seats in the December general election, despite fielding around 275 candidates.
Prime minister for six years from 2010, David Cameron called the vote on EU membership and led the so-called "Remain" campaign.
When the country backed Brexit, he had little choice but to resign, admitting he could not be "the captain that steers our country to its next destination".
Cameron has since stayed largely out of the limelight, but gave a flurry of interviews in September to mark the publication of his memoirs.
He has also insisted that he does not regret calling the vote, but deeply regretted Remain's defeat and the resulting divisions and crises.
The ex-prime minister did not back Brexit in 2016, but emerged as the "safe hands" candidate to lead the governing Conservatives after Cameron's departure.
May vowed Britain would leave the single market and end freedom of movement, but was severely weakened after she opted to hold a snap general election in June 2017, which saw the Conservatives lose their parliamentary majority.
She subsequently faced near-constant rebellions and chastening defeats, and eventually stepped down as leader last year – after parliament had rejected her Brexit divorce deal three times.
The former London mayor was a figurehead in the official Leave campaign, urging Britain to "take back control" from Brussels.
He was then made foreign secretary by May, but his two-year stint ended when he resigned over her Brexit strategy.
Johnson retained a high profile, using his weekly column in The Daily Telegraph to attack her approach, and was well-placed to take advantage when May eventually stood down.
He easily won a Conservative Party leadership contest in July, and then defied expectations by securing new divorce terms with Brussels.
He scored a thumping majority in a December general election on a pledge to "get Brexit done".
Johnson has vowed to finalise trade deals with both the soon-to-be 27-member EU, and the United States, in 2020.
The EU's chief Brexit negotiator has been ever-present in the process since Britain voted to leave the bloc, heading Brussels' team in the first phase of divorce talks.
The former French minister and veteran politician has been commended across Europe for his handling of the tricky and high-profile task and for keeping the other 27 members united behind his strategy.
The European Commission has asked Barnier –– an ex-EU commissioner well-versed in the mysteries of the bloc's law –– to remain in the post for the next stage of negotiations.