As the gray dawn came up over London on the morning of June 9, 2017, Theresa May had one urgent mission: to stop Jeremy Corbyn from becoming prime minister.

May was hunkered down inside her Conservative Party's headquarters with her closest aides, trying to make sense of the shocking failure of her campaign to win a snap general election. By 4:30 a.m. it was clear she'd lost her majority, and the socialist Labour Party leader was within striking distance of replacing her in government.

May held on — just — and has battled for 23 months at the head of a minority government. But the core policy she's been fighting to implement — an orderly divorce from the European Union — now rests in the hands of the man she fought to keep from power.