Boris Johnson is quitting as Tory leader after ministers and MPs made clear his position was untenable. He will remain as Prime Minister until a successor is in place, expected to be by the time of the Conservative Party conference in October.
A No 10 source said Mr Johnson spoke to Sir Graham Brady, chairman of the Conservative 1922 Committee, to inform him of his decision: "The Prime Minister has spoken to Graham Brady and agreed to stand down in time for a new leader to be in place by the conference in October.”
The resignation comes after the Prime Minister haemorrhaged support among his ministers and MPs. More than 50 MPs have resigned from government or party roles since Tuesday night, when the mass exodus was triggered by the resignations of Rishi Sunak and Sajid Javid from the Cabinet.
The Prime Minister had sought to defy his critics and carry on in office, despite warnings from Cabinet colleagues that this was not sustainable. However, resignations continued and Chancellor Nadhim Zahawi - who was only appointed to the role on Tuesday - went public with his call for the Prime Minister to quit.
As Mr Johnson steps down, what does this mean for the role of Prime Minister and the Tory leadership? Here’s a look at how the process might play out.
What happens when the Prime Minister resigns?
The 1922 Committee, a powerful backbench committee chaired by Sir Graham Brady, has the ultimate responsibility for setting the rules in any Conservative Party leadership contest.
Leadership elections only happen if a Conservative leader resigns or if they lose a vote of confidence among MPs. Now that Mr Johnson has resigned, a leadership contest will be held to replace him as Tory leader.
In his resignation speech outside Downing Street, Mr Johnson said that he had agreed with Sir Graham "that the process of choosing that new leader should begin now and the timetable will be announced next week".
That timetable, agreed by the 1922 Committee and Tory Party HQ, will likely see a new Tory leader in place before the party conference in October. It is difficult to know at this stage how long the contest will last, with the exact timetable to be revealed next week, but the process to replace Theresa May in 2019 took about 40 days. Some Tory MPs have expressed an eagerness to accelerate the process to have a new leader in place as soon as possible.
Both Tory MPs and Conservative Party members play a decisive role in electing the next leader. Tory MPs will whittle down the candidates to a final two through a balloting process, with party members then voting on which of the two candidates they would prefer.
BBC News reported that several Conservative MPs are pushing for Boris Johnson to leave office immediately. This would require an interim ‘caretaker’ Prime Minister to be appointed. Currently, Dominic Raab is the Deputy PM and therefore the logical choice in this case.
However, if Mr Raab decided to stand for Conservative leadership, this would be seen as an unfair advantage and a more neutral interim Prime Minister would be found instead.
Additional reporting by PA.