Prime Minister of the United Kingdom the incumbent is consistently ranked as one of the most powerful and influential people in the world. The Prime Minister is the head of the United Kingdom government. As such, the modern Prime Minister leads the Cabinet (the Executive). In addition, the Prime Minister leads a major political party and generally commands a majority in the House of Commons (the lower House of the legislature). The incumbent wields both significant legislative and executive powers. Under the British system, there is a unity of powers rather than separation. In the House of Commons, the Prime Minister guides the law-making process with
House of Commons of the United Kingdom Thus, whenever the office of prime minister falls vacant, the Sovereign appoints the person who has the support of the House, or who is most likely to command the support of the House—normally the leader of the largest party in the Commons, while the leader of the second-largest party becomes the Leader of the Opposition. Since 1963, by convention, the prime minister is always a member of the House of Commons, rather than the House of Lords. The Commons may indicate its lack of support for the Government by rejecting a motion of confidence or by passing a motion of