With Boris Johnson announcing his resignation on Thursday, we look at what could happen next.
What happens now?
Johnson announced that he would resign but proposed remaining as a caretaker prime minister until Conservative MPs have chosen a new leader, possibly until the autumn.
But it is not certain that this will happen, in which case it is possible a caretaker prime minister could be installed while the party leadership election process takes place.
Could the deputy prime minister, Dominic Raab, be a caretaker PM?
Raab has performed that function before, when Johnson was ill with Covid in spring 2020. However, the caretaker should not be a candidate for the leadership and would have to excuse himself if he decided to stand.
Who else could be a caretaker?
Some Conservatives have called for Theresa May to return as a caretaker. Senior cabinet ministers could also play this role.
How would a new prime minister be chosen?
First by Conservative MPs and then by party members. It is for them to determine a Tory leader, who is then prime minister as the party has a Commons majority.
To take part in the race, a Tory MP has to be nominated by eight colleagues.
Once all the candidates have declared, Tory MPs will hold a series of votes until only two remain. In the first round, candidates must get 5% of the votes to stay in the running, which is 18 votes.
In the second round they must get 10%, which is currently 36 MPs. In the following rounds, the candidate with the least number of votes is eliminated until two candidates remain.
When two MPs are left in the race, party members get to make their final choice before a deadline set by the 1922 Committee.
How long will the whole process take?
In 2019, when Johnson replaced May, the entire leadership process took about six weeks.
Assuming the new leader was able to command the confidence of the Commons, they would not be required to call a general election.
Who has said they will stand to be PM?
Many senior MPs are expected to put their names forward, including Rishi Sunak, Liz Truss, Penny Mordaunt, Ben Wallace and Sajid Javid. So far, the attorney general, Suella Braverman, has said she intends to stand, while the veteran Brexit campaigner and backbench fixer Steve Baker has said he is being urged by colleagues to do so. The chair of the foreign affairs select committee, Tom Tugendhat, and the former minister Jake Berry have also indicated they will stand.
Could Johnson stand again?
It would be a highly controversial move given that Johnson has told Sir Graham Brady, the head of the 1922 Committee, that he would continue only until a new leader is in place.
In his resignation statement he said: “I’ve agreed with Sir Graham Brady, the chairman of our backbench MPs, that the process of choosing that new leader should begin now and the timetable will be announced next week.
“And I’ve today appointed a cabinet to serve, as I will, until a new leader is in place.”
What powers does Johnson still have?
Until he officially gives up the office of prime minister, Johnson still has the same powers, in theory. Given the backlash from across the party over the last few days, he now lacks the authority to introduce any radical new policies.
He could still represent the UK abroad – he may find time for an extra trip to Ukraine – and can continue to make public appointments or changes to his team of ministers.
One of his final acts in office is likely to be submitting his honours list of knighthoods and appointments to the House of Lords.
This would include the advisers, ministers and donors who have served him during his political career.