Prime Minister of the United Kingdom

The prime minister of the United Kingdom is the head of government of the United Kingdom. The prime minister advises the sovereign on the exercise of much of the royal prerogative, chairs the Cabinet, and selects its ministers. Modern prime ministers hold office by virtue of their ability to command the confidence of the House of Commons, so they are invariably members of Parliament.

The office of prime minister is not established by any statute or constitutional document, but exists only by long-established convention, whereby the monarch appoints as prime minister the person most likely to command the confidence of the House of Commons. In practice, this is the leader of the political party that holds the largest number of seats in the Commons. The prime minister is ex officio also First Lord of the Treasury (prior to 1905 also the official title of the position), Minister for the Civil Service, the minister responsible for national security, and Minister for the Union. The prime minister's official residence and office is 10 Downing Street in London.

Early conceptions of the office of prime minister evolved as the primus inter pares ("first among equals"); however that does not differentiate on status and responsibility upon whoever is holding office. Historically, the prime minister has never been the first among equals at any time prior to 1868. Until now, that characterisation of the prime minister is reflective of the democratic nature of their position. The power of the prime minister depends on the support of their respective party and on the popular mandate. The appointment of cabinet ministers and granting of honours are done through the prime minister's power of appointment. The prime minister alongside the cabinet proposes new legislation and decides on key policies that fit their agenda which are then passed by an act of parliament.

The power of the office of prime minister has grown significantly since the first prime minister, Robert Walpole in 1721. Prime ministerial power evolved gradually alongside the office itself which have played an increasingly prominent role in British politics since the early 20th century. During the premierships of Margaret Thatcher and Tony Blair, prime ministerial power expanded substantially, and their leaderships in the office were described as "presidential" due to their personal wielding of power and tight control over the cabinet. The prime minister is one of the world's most powerful political leaders in modern times. As the leader of the world's sixth largest economy, the prime minister holds significant domestic and international leadership, being the leader of a prominent member state of NATO, the G7 and G20.

As of 2025^[update], 58 people (55 men and 3 women) have served as prime minister, the first of whom was Robert Walpole taking office on 3 April 1721. The longest-serving prime minister was also Walpole, who served over 20 years, and the shortest-serving was Liz Truss, who served seven weeks. Keir Starmer succeeded Rishi Sunak as prime minister on 5 July 2024, following the 2024 general election.

The position of prime minister was not created but evolved slowly and organically over three hundred years due to numerous Acts of Parliament, political developments, and accidents of history. Therefore, the office is rarely found in any statute and according to the Political and Constitutional Reform Committee in 2014: "It is impossible to point to a single point in history when the post was created or even a decision to create it."

The 17th century saw a transformative period in British history. The Union of the Scottish and English crowns followed by the Wars of the Three Kingdoms, including the English Civil War, saw the final conflict between the Monarchy and the parliaments (of England and Scotland) over governance, culminating in the end of absolute monarchy with the execution of Charles I in 1649. In 1660, the Monarchy was restored with the ascension of Charles II signalling a return to royal rule but with growing limitations. The Glorious Revolution of 1688–1689 led to the deposition of the Catholic James II and the establishment of William III and Mary II as constitutional monarchs. After a series of bills passed by the parliaments, such as the Bill of Rights and Claim of Right in 1689, the powers of the monarch were reduced, being replaced by the powers of parliament. The Bill of Rights established the supremacy of Parliament over the Crown and set up certain civil rights. During this period, Parliaments were dominated by two political factions: the Whigs and the Tories. The Whigs supported parliamentary sovereignty and constitutional monarchy while the Tories favoured the divine right of kings and the deposed James II. These two groups were considered by some to be "embryonic political parties."

The resulting English Constitution established in 1689 gave the English Parliament the power over the "purse" or the Treasury. The monarch who now could commit to and follow agreed policy allowed Parliament to pursue and fund its own policies without any fear of diversion of the funds. By this point, the Monarch was forced by incentive to cede power to Parliament under the credible threat of removal of any who ignored the Constitution.