What is the title of the most important minister in the British Parliament?

The British political system is structured around a Parliament, which is the supreme legislative body. Within this system, the government is led by the Prime Minister. Now, the title "Prime Minister" didn't just appear overnight; it evolved organically. Back in the 18th century, the King's chief advisors started gaining more power, and one of them, usually the First Lord of the Treasury, became seen as the leading figure. Robert Walpole is often considered the first Prime Minister, even though the title wasn't officially used then. The Prime Minister is essentially the head of the government, responsible for choosing the Cabinet and setting the government's agenda. While other ministers hold important positions, the Prime Minister is "first among equals," leading the executive branch. So, while "Head Minister" or "Head of Parliament" might sound plausible, they don't reflect the specific, historically developed role of the Prime Minister in the UK's political structure. The "House of Lords" is a chamber within Parliament, not a person.