A protester with 12 gold stars representing the European flag stars, as tears on her cheeks, takes part in a "Flag Mob" in Parliament Square in central London on February 20, 2017. JUSTIN TALLIS

The U.K. finally left the EU on Friday evening after 47 years of membership, marking one of the biggest political and economic shifts in modern European history. Brexit brings about the end of a tumultuous three-and-a-half year departure process that has caused turmoil in the U.K.'s political establishment, economic uncertainty and heightened tensions between the U.K. and the EU — its largest single trading partner as a bloc. The departure on January 31 also marks the start of a "transition period" in which the U.K. remains a member of the single market and customs union and begins negotiations with the EU to strike a free-trade deal. During the transition period, the U.K. will not have voting rights on EU matters but will still be bound by EU rules. The U.K. government has set an ambitious (and some say, unviable) deadline of the end of 2020 in which a deal must be reached, otherwise it will leave the single market with "no deal" and will have to revert to World Trade Organization rules.

How did this happen?

On June 23, 2016, the British people went to the polls in a vote on whether the U.K. should remain a member of the EU. To much of the country's shock — even, it appeared, to politicians like current Prime Minister Boris Johnson who campaigned to leave — 51.9% of Brits voted to leave the EU with 48.1% voting to remain in the economic and political union. Although the political earthquake was unexpected, euroskepticism was rife in the country in the decades and immediate years leading up to the referendum, fueled partly by an anti-EU tabloid press in the U.K. and the rise of the U.K. Independence Party led by Nigel Farage. A migration crisis in Europe in the run-up to the 2016 vote, fears over the possible accession of Turkey to the EU and a desire among many Brits to contain immigration also played a part. There were more intangible factors such as Britain being an island separated from its continental neighbors, and of somehow, someway, being "different." Reeling from the vote and the immediate resignation of then Prime Minister David Cameron, the government under Theresa May took until March 29, 2017, to trigger "Article 50," beginning what was meant to be a two-year countdown to the U.K. formally leaving.

The EU and U.K. then struck a Brexit deal, or "Withdrawal Agreement," but it failed to win approval by a majority of the British Parliament in March, 2019, and May was forced to ask the EU to extend the deadline. With her Brexit deal being rejected by a total of three times by Parliament, May was all but forced to step down as party leader last summer. Many point to a misjudged election she called in 2017 as being behind her downfall when she lost her paramilitary majority. Her departure prompted a leadership race within the ruling Conservative Party and the ascension of Brexit-supporting Johnson in July. Johnson went back to Brussels and renegotiated parts of the Brexit deal. His plan was also rejected by lawmakers in Westminster but a snap election in December gave him the crucial majority he desired and needed.

What happens next?

The U.K. will now remain a member of the EU's single market but only during a "transition period" until the end of 2020. During that time, the U.K. and EU will try to strike a trade deal, although the short time frame is seen as ambitious and Brussels has warned London that the trading relationship will not be the same post-Brexit. Irish Prime Minister Leo Varadkar suggested in an interview with the BBC Monday that the EU will be the "stronger team" in post-Brexit trade talks and that striking a deal would be "difficult." Johnson has dismissed pessimism, however, saying the U.K. can "wrap up" a deal by its self-imposed deadline. What's certain, and repeatedly reiterated by the EU side, is that the economic and political relationship will change and the U.K. might not enjoy the "frictionless trade" it has enjoyed as a member of the EU and a member of its single market. The single market seeks to guarantee the free movement of goods, capital, services, and labor — the "four freedoms" — within the EU. And with a collective population of over 500 million people and consumers, the value of single market membership and that unfettered movement of goods and services is a boon to businesses in the bloc.

Mixed feelings