Boris Johnson, Conservative leader, has resigned. However, he will remain as PM until the party selects his successor.
This could mean that a general election is necessary.
General elections in the UK - where all 650 MPs have been elected to the House of Commons -- must be held within five years.
Unless an earlier election is called, the next election won't be held until January 2025.
This is five years since the date the current Parliament met its first (17 December 2019), plus any time needed for an election campaign.
The prime minister usually makes the decision to hold early elections.
However, this was not the case until recently.
2011 saw the passage of a law that stripped the PM of the power to hold early elections and gave control to the House of Commons.
These rules stipulate that an early election can only be held if there are certain conditions, such as two-thirds of the MPs agreeing to one.
After winning the 2019 election the Conservatives introduced a new bill, the Dissolution and Calling of Parliament Act 2022. This law abolished previous laws and restored the traditional power of the PM to call elections at any time they choose.
The Conservative Party must now choose a new leader after Mr Johnson has resigned. The next PM will be chosen by the winner of this contest.
The new PM is not required to call an election early, but they could if they wanted.
For example, Gordon Brown did not hold an election when he took over as Labour Prime Minister Tony Blair in 2007.
A PM can request an early election by making a "request to the Queen" for dissolution of Parliament. This is the official term to close Parliament to hold an election.
After an election has been called, polling day is expected to be held 25 days later.
At this point, MPs are removed from their position and can run for re-election (assuming that they decide to stand again).
The PM must "request" permission to the Queen. In theory, she could reject it.
It is not clear what circumstances might lead to the Queen doing this. A government document known as "dissolution principles", outlines the conditions under which the PM may ask the Queen to hold an early election.
According to Catherine Haddon, a representative of the Institute for Government, principles that would allow Queen Elizabeth to decline an early election request have never been tested in cold light.
Meg Russell, Director of the Constitution Unit, concurs: "There's a tacit acceptance" that the Palace plays a role.
"So, the question is: "Under what circumstances would she block it?" It would be politically problematic.
