Despite resigning as head of the Conservative Party, Boris Johnson still remains in Britain's top job as "caretaker prime minister".
His plan to continue in the role until a new leader is found follows British convention and the process set by his predecessors.
But it has sparked rumblings from some quarters of his own party that Mr Johnson should not remain in power and instead leave immediately.
Some MPs have suggested his position is untenable given the collapse of his cabinet's support last week.
Former prime minister John Major, who took over after Margaret Thatcher resigned from office, is among those who have called on the 1922 Committee to change the rules and remove Mr Johnson as caretaker.
Mr Major released a letter saying it would be "unwise" and "unsustainable" for Mr Johnson to remain in the top job for "up to three months".
"Some will argue that his new cabinet will restrain him. I merely note that his previous cabinet did not — or could not — do so," he wrote.
So, could Mr Johnson actually be kicked out of the role of caretaker? Here are what rules would have to change for him to be removed before a new leader is chosen, and how that could play out.
The Conservative rebellion to remove Johnson as caretaker
The timetable for the process of appointing the next prime minister will be announced this week, with some estimates it could stretch out to September or October, when the Conservative Party conference in set to be held.
Reports suggest the party is planning to whittle down candidates to the final two by July 21, and have the new leader decided by September.
That would also follow a similar timeline to the previous ballot, which took 46 days after Theresa May resigned.
But other Conservative Party members, including Mr Major, have questioned whether Mr Johnson should stay in office that long after the chaos of the last few days, weeks and months.
Conservative Simon Hoare said the Prime Minister's behaviour meant he had forfeited the right to remain as a caretaker leader.
George Freeman, who resigned as science minister on Wednesday, said it was "difficult" to see how Mr Johnson would be able to "put together a government that next week will escape from the insecurity and chaos we've seen this week".
"I just worry that he isn't going to be able to bring the stability that we need," he told Sky News.
"He's got a Chancellor who's already said he doesn't have any confidence in him and two or three other members of the cabinet.
"The Attorney-General is outwardly campaigning for his job. It's just not a credible way to form a government."
Others have called for the process of appointing the next leader to be sped up.
Former minister Sir Bob Neill has asked whether it "might it not be in everybody's interest to speed up the transition as much as possible, while Kwasi Kwarteng, the business secretary, said the Tories needed "a new leader as soon as practicable".
This little-known committee could play a crucial role
The timetable for the leadership contest is not in the prime minister's hands, but up to a little-known group called the 1922 Committee.
The parliamentary committee, formally known as the Conservative Private Members' Committee and sometimes referred to as the "men in grey suits", represents the rank-and-file party members and governs party rules.
It decides when key votes take place and runs the parliamentary proceedings to narrow the candidates down to two contenders for a vote.
Mr Major has argued that one way to speed up Mr Johnson's departure would be to eliminate a vote of party members and let only MPs decide who should become the next leader.
Under the current rules, the two candidates are put in a postal ballot of the wider Conservative Party membership, with the winner named as prime minister. That process can take up to about six weeks to complete.
So far, the committee has avoided making any rule changes, with sources telling Reuters before Mr Johnson resigned that they were waiting for a new mandate following fresh elections of the committee's executive tomorrow.
Even if the committee decides to make no changes, Mr Johnson could still face pressure from the opposition this week.
If Johnson isn't removed, UK Labour may try to bring on an election
Mr Johnson could face a vote of no confidence in parliament.
Labour leader Sir Keir Starmer has warned he will try to bring on a national election using a vote of confidence in the prime minister this week unless Conservatives remove Mr Johnson earlier.
"We can't go on with this prime minister clinging on for months," he said.
To pass, the no-confidence motion would require a number of Conservative MPs, who hold a large majority in parliament, to back Labour.
Given some Conservatives have publicly stated they want to "keep the wheels of government turning", it appears unlikely such a vote will succeed.
But Conservatives have floated one other option to replace Mr Johnson as caretaker.
Could an interim PM be appointed?
Mr Major has also suggested installing an interim PM to replace Mr Johnson as caretaker, such as Dominic Raab, who stepped in as deputy prime minister when Mr Johnson was sick with COVID-19 in 2020.
An interim prime minister is a member of the cabinet who temporarily acts as prime minister when the leader is unable to do so.
Along with Mr Raab, Mr Johnson's predecessor Theresa May has also been named as a possible interim replacement.
But the former prime minister was doubtful when asked about the possibility, saying she "didn't think there's going to be a caretaker prime minister in the sense of somebody else coming in".
There is no constitutional precedent for an interim prime minister being installed as a caretaker PM following a resignation.
ABC/Reuters
