Liz Truss announced her resignation on October 20 after just 44 days in office - making her Britain's shortest-serving prime minister ever.
The Tory leader announced that she would be leaving the role after weeks of turmoil in Downing Street and furious backbench MPs expressing no confidence.
Truss took over from Boris Johnson on September 5 after beating former Chancellor Rishi Sunak and current Leader of the House of Commons Penny Mordaunt in the leadership contest, which took place over the summer.
Johnson handed in his letter of resignation on July 7 amid countless scandals, but clung on to the role of PM until a new leader was found.
Now Johnson wishes to run as Tory leader again, according to political insiders - and he's even previously dropped hints about returning to Downing Street.
But will he be able to become prime minister for the second time? Here's everything you need to know.
How many times can someone be prime minister?
There is no limit on how many times someone can be prime minister.
In British history, only two people have been prime minister more than once - Labour ’s Harold Wilson and Conservative Sir Winston Churchill.
Wilson was the first PM to make a comeback as leader, with his first stint between October 1964 and June 1970, and his second between March 1974 and April 1976.
Churchill was PM for the first time between 1940 to 1945, during the Second World War, and again from 1951 to 1955.
Can Boris Johnson become prime minister again?
As ex-prime ministers are allowed to run for office as many times as they like, it is a possibility that Johnson could become PM once again follow Truss' exit.
A number of Conservative MPs have already publicly shown support for Johnson's potential return, including Nadine Dorries, Brendan Clarke-Smith and Michael Fabricant.
Brendan Clarke-Smith told Sky News: “What we need now, we need someone who can come in, who can bring people together, somebody who actually has that mandate, a mandate from the people at the last general election, a mandate from party members and somebody actually who can get this party going again, get us winning elections again.
“The only person that I think that ticks all those boxes is Boris Johnson.”
In Johnson's exit speech as PM, it seemed that he left the door open for a comeback.
In the speech, he said: “Like Cincinnatus, I am returning to my plough.”
Cincinnatus was a Roman statesman from the fifth century BC, who left his role to become a farmer.
However, he later returned to his role as military leader due to a crisis.
How long can a prime minister be in office?
Prime ministers are selected for a five-year term in the UK following a general election.
There is no limit on the number of terms a PM can lead for.
A PM can only lose their premiership if their party has a vote to change the leadership of their party, if their party does not win government at an election, or if they decide to resign.
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