Line ID: clementine88
I love it when Americans think they understand British politics.
Here, the Prime Minister is the leader of the largest party in the House Of Commons. The method by which they become leader of their parties varies by party, but suffice to say that all members of the party (not just MPs) get a vote. As an aside, the party leader still has to stand in their constituency, so it's not beyond possibility that they would be rejected by the electorate even if their party won the election.
"The Tokyo Rose of the Trailer Park"