This is how the next 72 hours are roughly due to play out.
At 12.30pm the winner of the leadership race will be revealed at an event at the Queen Elizabeth II Conference Centre in Westminster.
The venue, a short walk from parliament and Downing Street, was also where Jeremy Corbyn was announced as Labour leader in 2015.
But the new Tory leader will not take over as prime minister immediately.
This will be Boris Johnson’s last day in office as PM. In the early morning, around 8.30am, he will deliver a farewell speech in Downing Street.
Johnson will then fly from London to Aberdeen and make his way to Balmoral to see the Queen and resign.
The Queen will then meet with the new Tory leader and appoint them prime minister.
Truss – or Sunak if he pulls off a spectacular upset – will then fly to London and deliver their first speech as PM outside No.10 at about 4pm.
It is then expected the that the new cabinet will be formed over the course of the next few hours.
Parliament returns from its long summer recess this week, which means the new PM will face Labour leader Keir Starmer at PMQs after about only 24-hours in the job.
Later in the week
But the likely incoming PM has not said what form any help will take or given a precise date when she will unveil any plan.