To be prime minister you have to have support of 50%+1 of the MPs. This means either having them in your party, or having a deal with another party.

You also have to be an MP.

Currently Kier Starmer is a Labour mp in an area of London. He’s resigning and is being replaced by someone (Burnham) who was Labour Mayor for Manchester, but stood as MP in an area of Manchester last month after another Labour MP resigned.

Burnham beat reform in that election, and Count Binface. There was a discussion thy given how unpopular Labour is, that reform might win. In the end everyone who was anti reform (Farage’s party) voted Burnham and he got 55% of the vote.

While the sentiment in the U.K. is that if a general election were held tomorrow, Farage would win his seat, and reform would win a large number of votes. In reality polling puts Farage’s party around 25%, with four other parties on 10-20%. As the election isn’t proportional though it’s possible reform could get 55% of the seats with 25% of the vote, however last time they got 1% of the seats with 12% of the votes.

You also have to be an MP.

I don't think that's strictly true. You definitely don't have to be an MP in order to hold a cabinet office. I think that extends to the PM as well. It's never been tried obviously.

That's very informative, thanks!