David Cameron resigned as British prime minister after his Remain side lost the Brexit referendum. Brexiteer Boris Johnson was tipped to succeed him but ultimately didn't run. Michael Gove, another Leave campaigner, made his own bid to be leader but was eliminated in the second round of voting. Fellow Brexiteer Andrea Leadsom - who was Mrs May's last remaining rival - withdrew to avoid a leadership contest that could destabilise Britain after the Brexit vote. Mrs May's victory may not have provided much stability in the years that followed, but that's how the reluctant Remainer gained power.
At the start of her tenure Mrs May enjoyed a majority - albeit a small one - in the House of Commons. In April 2017, she made the fateful decision to hold a snap election, arguing that Britain needed "strong and stable" government due to Brexit. Her party was ahead of Jeremy Corbyn's Labour in the polls and she claimed he'd lead a "coalition of chaos" if he won. However, the Conservatives had a poor campaign and Labour performed much better than expected. The June 2017 election saw Mrs May lose her Westminster majority.
After the election result, the British media was forced to explain to the public there who Arlene Foster's DUP are. That's because the DUP's 10 MPs held the balance of power and Mrs May did a deal with them that allowed the Tories to stay in government.
Mrs May promised £1bn in extra spending for Northern Ireland in return for support in certain votes. The arrangement has been a thorn in Mrs May's side in recent weeks as the DUP opposes her Brexit deal.
Mrs May's first party conference speech after the 2017 election came amid rumblings of leadership challenges and was a disaster. Firstly a prankster interrupted Mrs May to hand her a P45 that he claimed Boris Johnson had asked him to give her. Mrs May also coughed her way through much of the address and was given a cough sweet at one point by Chancellor Philip Hammond. Finally letters from the slogan 'Building a Country that Works for Everyone' began falling off the wall behind her. In contrast, Mrs May danced on stage to the tune of Abba's 'Dancing Queen' at this year's conference. She was poking fun at her own awkward dance moves during a trip to Africa.
After 18 months of tough UK-EU negotiations the Withdrawal Agreement was to go to a vote in the House of Commons on Tuesday. With large sections of the Tories, as well as Labour and the DUP, opposing the deal, it had little chance of passing. Senior ministers were insisting the vote would go ahead just hours before it was cancelled on Monday. Mrs May went on a tour of EU capitals in a bid to win concessions while at home members of her own party forced a no-confidence vote.