On Monday, Liz Truss is expected to be unveiled as Britain's next prime minister after a closely contested race with Rishi Sunak.
Here is a timeline of how the new prime minister's first few days are likely to play out:
12.15pm: Either Liz Truss or Rishi Sunak will be announced as the winner of the Tory leadership contest at the Queen Elizabeth II Conference Centre in Westminster.
Afternoon and evening: The winner finalises their choices for their Cabinet and wider ministerial roles, and writes their prime ministerial speech.
8.30am: Boris Johnson makes his farewell speech on the steps of No 10. He then departs Downing Street for the last time and flies to Aberdeen airport.
Early morning: Mr Johnson's successor flies up to Aberdeen on a separate plane in readiness to meet the Queen.
Late morning: Mr Johnson arrives at Balmoral, where the Queen is currently staying. He will be ushered into the Drawing Room, where for the first time in history a prime minister will relinquish his role.
Early afternoon: After Mr Johnson has departed, his successor will arrive at Balmoral, where they will be invited in to see the Queen and be appointed as Britain's next prime minister.
2pm: The new prime minister flies back to London. On the plane, they could be briefed by officials on national security matters they need to know as prime minister.
4pm: They will arrive in Downing Street and make their first speech as prime minister.
Later on Tuesday afternoon: The new prime minister makes senior Cabinet appointments and holds further meetings with civil servants.
They will receive the nuclear codes and write "letters of last resort" to commanders of Trident-carrying submarines with instructions for what to do in the event of Britain and its Government being wiped out by a nuclear attack.
Tuesday evening: The new leader will take congratulatory phone calls from world leaders. Ms Truss has said her first call will be to Ukraine's President Zelensky.
Morning: First meeting of the new Cabinet.
12pm: The new PM will lead their first Prime Minister's Question Time, facing Sir Keir Starmer.
Afternoon: Appointment of junior Government ministers and further briefings from officials including the Cabinet Secretary to complete the hand-over of powers.
Congratulatory phone calls from world leaders continue.
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