After Boris Johnson was ousted by his colleagues following a slew of scandals, 11 Tory MPs ran to replace him.
Ballots of Conservative MPs whittled them down to two: Liz Truss and Rishi Sunak.
The pair have battled it out over the last few weeks for the backing of voting party members, going head-to-head in 12 official hustings.
Either Ms Truss or Mr Sunak will emerge as the winner next week.
Here is a timeline of events:
– September 2, 2022
Voting in the Tory leadership contest closes at 5pm on Friday.
Ballots were sent to Tory party members via post between August 1 and August 5. Any ballots received after 5pm on September 2 will not be counted, the Conservative Party website states. Online voting is possible until close of ballot.
– September 5, 2022
The candidate who receives the most votes from Tory party members will become the new Conservative Party leader, and therefore Prime Minister.
The winner of the contest will be announced on Monday – the date when Parliament returns – by Sir Graham Brady, chairman of the 1922 Committee of Conservative backbench MPs.
The new leader – widely expected to be Ms Truss – is expected to make a speech following the announcement and then spend the rest of the day finalising their choices for Cabinet and wider ministerial roles and writing their first prime ministerial speech.
Mr Johnson will remain Prime Minister until the following day.
– September 6, 2022
In a break with tradition, Mr Johnson and his successor will go to Balmoral in Aberdeenshire for the appointment of the new Prime Minister, rather than Buckingham Palace.
Under normal circumstances, the pomp and drama of the appointment is mostly confined to London over the course of an afternoon.
The outgoing premier typically makes a statement outside No 10 before a short journey to Buckingham Palace to formally resign to the Queen, who then swiftly welcomes and appoints the new Prime Minister before they return to Downing Street.
A palace spokesman confirmed on Wednesday that, this time, the Queen will welcome them at her Aberdeenshire retreat, heightening concerns about the health of the 96-year-old monarch.
Both Mr Johnson and his successor will have to make the 500-mile journey to Scotland, marking a major change in the normal choreography of the handover.
Mr Johnson is expected to make a farewell address outside 10 Downing Street at around 9am on Tuesday.
It is unclear how he will make the journey to Balmoral and whether he and his replacement will travel together.
If they take a plane – a journey that would likely take only a couple of hours – Mr Johnson could formally tender his resignation by around 11.30am.
The Queen will then appoint his successor – possibly by noon – and ask them to form an administration.
The new Prime Minister is expected to fly back to London and arrive at Downing Street to address the nation for the first time as PM by mid-afternoon.
After that, they will be expected to make senior Cabinet appointments and hold meetings with senior civil servants to be given nuclear codes, and for updates on matters of national security.
The change in procedure could delay the highly-anticipated reshuffle, which could potentially be pushed into the late evening if the new Prime Minister wants to meet and greet their new team from London as opposed to over the phone.
As constitutional expert and Institute for Government fellow Dr Catherine Haddon has suggested, the change could see appointments announced in “batches” throughout the rest of the week.
It is also likely to have a knock-on effect on the time and place of briefings and congratulatory phone calls, with the new premier being forced to potentially work on-the-move as they journey back to London.
– September 7, 2022
The new team is due to meet on Wednesday morning before the new premier faces their first Prime Minister’s Questions at noon.
Rishi Sunak during a leadership hustings hosted by GB News Peter Byrne
Liz Truss during GB News' Manchester hustings Peter Byrne