Prime Minister Theresa May on Friday said she would quit, triggering a contest that will bring a new leader to power who is likely to push for a more decisive Brexit divorce deal.
Mrs May set out a timetable for her departure: She will resign as Conservative Party leader on June 7 with a leadership contest in the following week.
"I will resign as leader of the Conservative and Unionist party on Friday, 7 June so that a successor can be chosen," Mrs May said outside 10 Downing Street.
Mrs May, once a reluctant supporter of EU membership, who won the top job in the turmoil that followed the 2016 Brexit vote, steps down with her central pledges - to lead the United Kingdom out of the bloc and heal its divisions - unfulfilled.
What has May said about her departure?
The Prime Minister initially quelled the calls to resign as far back as March, saying she would leave once her Brexit deal has passed.
Addressing the 1922 Committee at the time, Mrs May said: “I have heard very clearly the mood of the parliamentary party. I know there is a desire for a new approach – and new leadership – in the second phase of the Brexit negotiations – and I won’t stand in the way of that.
“But we need to get the deal through and deliver Brexit. I am prepared to leave this job earlier than I intended in order to do what is right for our country and our party.
“I ask everyone in this room to back the deal so we can complete our historic duty – to deliver on the decision of the British people and leave the European Union with a smooth and orderly exit.”
But as the weeks ticked by and there was little sign her deal would be passed, frustration grew within her party once again.
On May 16, the prime minister was forced to agree to stand down within weeks so the Conservatives can elect a new leader before Parliament’s summer recess.
Mrs May agreed that she will announce the date of her departure after a vote on her Brexit bill in the first week of June, regardless of whether it is passed by MPs.
But support for Mrs May from some members of her Cabinet evaporated after ministers were shown a draft version of the Withdrawal Agreement Bill, which explicitly laid out a path to a legally-binding second referendum.
Standing down on Friday, she said: "I will shortly leave the job that has been the honour of my life to hold. The second female prime minister, but certainly not the last.
"I do so with no ill will but with enormous and enduring gratitude to have had the opportunity to serve the country I love," Mrs May said, with her husband, Philip, looking on.
What happens now she has stepped down?
Mrs May's announcement has now triggered a leadership contest.
She will stay on in a "caretaker" role to give the party long enough to pick a new leader. That's what David Cameron did in 2016 after the EU referendum in 2016.
If several names are put forward to lead the party, then a vote is held among Conservative MPs using the first past the post system to whittle down the field with the candidate with the fewest votes removed. Another ballot among Conservative lawmakers is then held until two candidates remain.
The final two nominees are then put to a ballot of the wider Conservative Party membership with the winner named the new leader.
Following David Cameron’s decision to step down as prime minister and Conservative leader after the EU referendum in 2016, five candidates put their names forward.
The field was narrowed to Mrs May and Ms Leadsom but she pulled out of the race before members voted, leaving May to become leader unopposed.
Who will replace Theresa May?
Here are the latest odds on who could become the next Conservative Prime Minister when Theresa May steps down.
Will there be a general election?
Probably not, as there is no obligation for the new leader to call an election.
Mrs May didn't call an election immediately when she was installed as prime minister and had repeatedly insisted she would not seek a general election before the scheduled 2020 poll.
She changed her mind in April 2017, claiming that divisions at Westminster risked hampering the Brexit negotiations.