David Cameron has announced he is stepping down as Prime Minister and leader of the Conservative Party.
He wants the new leader installed by October 2 when the party begins its autumn conference.
So how does the Conservative Party elect its leader? Here are the stages:
Nominations for leader come from Conservative MPs. If only one nomination is received, the leader is duly declared. If two are received, both names are put to a ballot of party members across the UK.
If three or more people are nominated, then a ballot of the 330 Conservative MPs is held "on the Tuesday immediately following the closing date for nominations" to whittle the pack down to two.
Second: Postal ballot
Once two front runners have been selected, the candidates then go head to head in a postal ballot of the wider party membership, which according to a House of Commons Library report stands at around 149,800 people.
This means the next Tory leader - and Prime Minister - could be elected into office on the votes of just tens of thousands of people.
Not much is known at the moment but Boris Johnson is the odds on favourite to be the next PM, followed by Michael Gove.
It will be up to the new leader if they call a snap election to bolster their position, or take over the leadership of the country on the say-so of their party members alone.
The chairman of the 1922 committee, currently Graham Brady, acts as the returning officer in the elections.
As such, he decides the date by which ballots have to be returned and the count commences that day.