The politician, whose shaggy, unkempt appearance does little to mask fierce personal ambition, has broken with Prime Minister Theresa May over Britain's exit from the European Union — he favors a much harder, more radical break with the bloc — just as he fell out with college chum and Prime Minister David Cameron in 2016 when Johnson made the fateful decision to jump on the Brexit bandwagon.
The foppish Johnson — an articulate campaigner — helped lead Brexit forces to victory in the June 2016 referendum that effectively ended Cameron's career and set in motion more than two years of tortuous negotiations with the EU.
Now that he has resigned, and is no longer required to show loyalty to May, Johnson is likely to focus on his long-term goal of becoming prime minister. He is one of the most visible and vocal figures in the Conservative Party, but he has made more than a few enemies along the way, and no one knows if he can ultimately get the party's backing for the top spot the next time a vacancy arises.
His last big gamble came in February 2016, when he dramatically parted ways with Cameron. The safe course for the ambitious former London mayor would have been to back his longtime political ally Cameron's bid to keep Britain inside the EU in the referendum and let the prime minister sink or swim.
Instead, Johnson decided to lead the "leave" campaign and use his considerable clout to try to pry Britain out of the EU and, at the same time, push Cameron underwater — a tactic that eventually worked, even if it was May, and not Johnson, who moved into 10 Downing Street after the moving vans took Cameron's furniture away.
The 54-year-old Johnson has managed to use his disarranged, slightly comical hair as a helmet, shielding him from more serious scrutiny. It lets him come across as an unconventional politician even as he carved a straightforward political path, moving from elite colleges into journalism, then Parliament, then City Hall, finally back to Parliament and ultimately a major Cabinet position.
He is (almost) always willing to play the buffoon, not minding when he's photographed stranded on a zip line looking ridiculous and happy to speak extremely elementary Greek to Greek constituents. Johnson emphasizes his American connections with American visitors (he was born in New York City's posh Upper East Side) and talks comfortably about his Turkish great-grandfather with Muslims, sometimes pointing out that his ancestor studied the Quran.
Throughout his career, Johnson has managed to surmount the sort of gaffes that have brought other politicians down. In his newspaper days, Johnson called Africans "piccaninnies" and referred to people from Papua New Guinea as cannibals. As a member of Parliament, he offended an entire British city when he complained that people from Liverpool were wallowing in "victim status" after a Liverpudlian was taken hostage and slain in Iraq.
He has apologized — a lot — and seems to have been forgiven, a lot. Now he can add a stint as foreign secretary to his resume — and not many expect him to leave it at that.