The United Kingdom is a unitary parliamentary democracy under a constitutional monarchy. King Charles III has been head of state since 8 September 2022, and Andy Burnham of the Labour Party has been Prime Minister and head of government since 20 July 2026. Laws are made by a two-chamber Parliament at Westminster: the elected House of Commons, with 650 MPs, and the appointed House of Lords. There is no single written constitution. The rules come instead from statutes such as the Parliament Acts 1911 and 1949 and the Human Rights Act 1998, from court judgments and from long-standing convention. Since 1999, Scotland, Wales and Northern Ireland have each had their own elected legislature and government.
This guide follows power from the top down: the Crown, the Prime Minister and Cabinet, the two Houses of Parliament, the courts, and finally the devolved governments in Edinburgh, Cardiff and Belfast.
The Crown: King Charles III, monarch since 8 September 2022
Charles III became king when his mother, Elizabeth II, died on 8 September 2022. He was 73, which made him the oldest person ever to take the British throne, and he was crowned at Westminster Abbey on 6 May 2023. He is King of the United Kingdom and also of 14 other Commonwealth realms, including Canada, Australia and New Zealand.
In law, executive authority still belongs to the sovereign. In practice the monarch stays out of party politics, and almost every power of the Crown is used on the advice of ministers. These powers, known as the royal prerogative, include appointing the Prime Minister and other ministers, granting royal assent so that bills become law, summoning and dissolving Parliament, and tasks ranging from issuing passports to declaring war. The power to appoint the Prime Minister is the one the monarch exercises personally. The last time a monarch used real personal discretion in that choice was 1834. The modern convention is that the King appoints whoever is most likely to command a majority in the House of Commons.
The King and the Prime Minister meet every week, and what is said stays private. The monarch has a "right and a duty" to comment on government business, but by convention must in the end accept the government's decisions. This gradual limiting of royal power is usually traced back to Magna Carta in 1215, and it is why the Crown is often said to reign but not rule.
The Prime Minister: Andy Burnham at 10 Downing Street since 20 July 2026
No statute created the office of Prime Minister. It grew out of convention, and Robert Walpole, who took office on 3 April 1721, is counted as the first. As of 2026, 59 people have held the job. Walpole served longest, at more than 20 years, and Liz Truss served the shortest time, about seven weeks in 2022. The Prime Minister is also First Lord of the Treasury, which is why that title is engraved on the letterbox of 10 Downing Street, and Minister for the Civil Service.
The way the current Prime Minister reached office shows the system at work. Keir Starmer led Labour to victory at the general election of 4 July 2024. As his approval ratings fell, Andy Burnham, then Mayor of Greater Manchester, became the favourite to succeed him. Burnham was not an MP, and only an MP can realistically lead the government. On 14 May 2026 the Labour MP for Makerfield, Josh Simons, resigned to open the way. Burnham won the by-election in June with 54.8% of the vote. Starmer then announced his resignation, Burnham was elected Labour leader unopposed, and on 20 July 2026 the King appointed him Prime Minister. There was no general election: the government changed because the party holding a majority in the Commons changed its leader.
The Prime Minister picks the Cabinet, the senior committee of ministers who run departments such as the Treasury, the Home Office and the Foreign Office. Ministers answer to the House they sit in, through statements and question sessions, so most senior ministers are MPs. The civil service departments around Whitehall carry out policy, which is why "Whitehall" and "Westminster" are both used as shorthand for the UK Government.
The House of Commons: 650 MPs elected on 4 July 2024
The House of Commons is the centre of the system. Each of its 650 members represents one constituency, chosen by first-past-the-post, and a general election must be held at least once every five years. The 2024 vote was the first under the Dissolution and Calling of Parliament Act 2022, which returned to the Prime Minister the power to ask the monarch for an early dissolution, and the first in which voters in Great Britain needed photo identification.
The result showed how the voting system turns votes into seats. Labour won 411 seats and a majority of 172 on only 33.7% of the vote, the lowest share for any governing party on record. The Conservatives fell to 121 seats on 23.7%, their worst result ever. Reform UK took 14.3% of the vote but only five seats.
The Commons controls the government in ways the other chamber cannot. It votes on taxes and spending, and only the Commons can force a government out through a vote of no confidence. Under the Parliament Acts 1911 and 1949 it can pass a bill without the consent of the Lords after a delay of about a year. The 1911 Act also cut the maximum life of a Parliament from seven years to five.
The House of Lords after the end of hereditary seats in 2026
The upper house meets in the same Palace of Westminster, but no one is elected to it. Most members are life peers, appointed by the Crown on the advice of the Prime Minister; some sit for a party, while others sit as non-party crossbenchers. Up to 26 archbishops and bishops of the Church of England also sit there as the Lords Spiritual. Its size is not fixed: on 5 October 2026 it had 796 sitting members, more than the 650 in the Commons.
For centuries, hereditary peers made up most of the House. The House of Lords Act 1999 removed several hundred of them and left 92 seats as a temporary compromise. That compromise ended in 2026, when hereditary membership was abolished outright. Today the Lords works mainly as a revising chamber. It examines bills line by line, proposes amendments and can delay legislation, but it cannot block the Commons for good. Until 2009 it was also the country's highest court, through the Law Lords.
The Supreme Court at Middlesex Guildhall since 1 October 2009
The Constitutional Reform Act 2005 moved the top appeal court out of the House of Lords. The new Supreme Court opened on 1 October 2009 in Middlesex Guildhall, across Parliament Square from the Palace of Westminster. It is the final court of appeal for civil cases from the whole UK and for criminal cases from England, Wales and Northern Ireland. Most Scottish criminal appeals end in Edinburgh. Because the UK has three separate legal systems (England and Wales, Scotland, and Northern Ireland), the commission that selects its justices must ensure the court has knowledge and experience of each. Its President since 11 January 2020 has been Lord Reed, a Scottish judge, who has announced that he will retire on 10 January 2027.
The court's powers reflect the doctrine of parliamentary sovereignty. It can strike down secondary legislation that goes beyond the powers Parliament granted, but it cannot overturn an Act of Parliament. Under section 4 of the Human Rights Act 1998 it can instead issue a declaration of incompatibility, saying a law conflicts with the European Convention on Human Rights. Parliament is not obliged to act, but ministers can use a fast-track procedure to amend the law. The court also decides disputes over the limits of devolved power.
Holyrood, the Senedd and Stormont: devolved government since 1999
Since 1999, power over areas such as health, education and transport in Scotland, Wales and Northern Ireland has been devolved to their own institutions. England has no parliament of its own and is governed directly from Westminster, apart from regional mayors such as the one Burnham led in Greater Manchester. Each devolved government has a First Minister. The UK Parliament keeps reserved matters such as defence and foreign policy.
- Scotland: The Scottish Parliament at Holyrood in Edinburgh has 129 members. At its election on 7 May 2026 the Scottish National Party won 58 seats, seven short of a majority, and secured a fifth consecutive term. John Swinney of the SNP has been First Minister since May 2024.
- Wales: The Senedd in Cardiff Bay grew from 60 to 96 members for its 7 May 2026 election, the first under closed-list proportional representation. Plaid Cymru became the largest party for the first time, with 43 seats. Reform UK won 34, and Labour, which had led every Welsh government since 1999, fell to 9. Rhun ap Iorwerth of Plaid Cymru has been First Minister since 12 May 2026.
- Northern Ireland: Under the 1998 Good Friday Agreement, the Assembly at Stormont uses power-sharing. The First Minister and deputy First Minister hold a joint office, and neither can act without the other. Michelle O'Neill of Sinn Féin has been First Minister since February 2024, the first Irish nationalist to hold the post. Emma Little-Pengelly of the Democratic Unionist Party serves as deputy First Minister.
The 2026 devolved elections produced governments of three different parties in Edinburgh, Cardiff and Belfast, none of them Labour, while Labour holds a large majority at Westminster. This is how a unitary state with devolved powers works in practice: the UK Parliament could in theory legislate on any subject, but by convention it does not legislate on devolved matters without the consent of the devolved legislature. For how England, Scotland, Wales and Northern Ireland fit together as countries, see our guide to how many countries make up the United Kingdom. For the city where most of this power is concentrated, read about London as the UK's capital. And to compare Westminster with the system across the Irish Sea, which also grew out of it, see how the government of Ireland works.