David Davis, United Kingdom Secretary of State for Exiting the European Union:
The title is a mouthful and the task is even more challenging for Davis, a long-serving lawmaker and staunch Euroskeptic who served under Conservative Prime Minister John Major in bruising 1990s dealings with the EU.
The longtime advocate of Britain quitting the EU was a natural choice to lead the British government's new department overseeing the Brexit talks.
A former special forces reservist, Davis is expected to be a tough negotiator in Brussels. British newspaper The Guardian newspaper labelled him "the old knuckleduster leading Britain out of the EU."
Theresa May, British Prime Minister:
The 60-year-old prime minister emerged victorious from a bitter and divisive leadership battle after her predecessor, David Cameron, quit following Britain's vote a year ago to leave the EU.
But her leadership has been thrown into doubt after her decision to call an early election in order to bolster her hand in Brexit negotiations backfired spectacularly this month. Her Conservative Party's comfortable majority in the lower house of the British Parliament evaporated following a lackluster campaign.
While May supported Britain remaining in the EU, since taking office she has pledged that "Brexit means Brexit."
Boris Johnson, British Foreign Secretary:
Britain's shaggy-haired foreign minister is a Latin-quoting maverick and former journalist who once compared the EU to Adolf Hitler in trying, "by different methods," to create another super-state.
It is hardly shocking, then, that Johnson was a prominent leader of the successful referendum campaign to take Britain out of the EU. What was surprising was May's decision to appoint a man known for his countless gaffes as her country's top diplomat.
"I wish it was a joke but I fear it isn't," former Swedish Prime Minister Carl Bildt tweeted last year when May made Johnson her foreign minister.
Michel Barnier, Chief Negotiator - Task Force for the Preparation and Conduct of the Negotiations with the United Kingdom under Article 50:
If anything, the title is even more of a mouthful than Davis's and in theory, Barnier has a more complex job in trying to reconcile the whims of 27 member states and face Britain with one voice.
A mountain man from France's southeast, he made a name for himself as co-president of the 1992 Albertville Winter Olympics.
The 66-year-old has served four times as a minister in a French government, under presidents Jacques Chirac and Nicolas Sarkozy.
He was also twice European Commissioner and supervised the reform of the European banking system following the financial crisis that started in 2008. He was said to be the most hated man in the City of London's financial district for his efforts to apply EU regulation in Britain. It is a reputation he does not want to live up to.
Donald Tusk, European Council President:
So far, so good, for the head of the EU summits, who must make sure that all 27 nations show no divisions during the talks. In a bloc where member states persistently disagree on everything from finances to migration, Tusk has been able to ensure remarkable unity in the face of Brexit, the biggest challenge in the EU's 60-year history.
The 60-year-old Pole has combined steely resolve in consultations with a human tough in personal relations to keep in line the political left and right and the geographic North and South. When he wants to, he speaks frankly of what is at stake for Britain and the need to stick to strict deadlines.
He was re-elected to his post in March, warmly endorsed by all — except the conservative government of his native Poland.
Jean-Claude Juncker, European Commission President:
With a different style to Boris Johnson's, Juncker is a master in his own right of blunt quips and deadpan humor. He's labeled one EU leader a "dictator" and threatened to call for the independence of Texas if U.S. President Donald Trump continues to criticize the EU.
But make no mistake: the Luxembourger is a canny political survivor who reached the EU's pinnacle from his tiny Grand Duchy of barely half a million people through shrewd alliances and an instinct for political survival.
His Commission, the EU's executive branch, is leading the Brexit talks and Juncker is bound to leave his prints on any outcome.