How Britain governs itself without writing the rules down

What it means to have no written constitution

The constitution of the United Kingdom is uncodified. It is made up of constitutional conventions, statutes and other elements, with no single document that could be handed to a reader as the constitution, and no procedure for amending it that differs from the procedure for passing any other law.

The organising principle is parliamentary sovereignty, which Parliament itself states in three parts: Parliament is the supreme legal authority in the United Kingdom and can create or end any law; the courts generally cannot overrule its legislation; and no Parliament can pass laws that future Parliaments cannot change. That third clause is the one with the most consequences. A written constitution puts some rules beyond the reach of an ordinary majority, and this arrangement does the opposite by design.

The system that results is called the Westminster model, and it has been adopted by many countries that were formerly parts of the British Empire, and it has been copied without ever having been written down.

What holds it together instead is convention: unwritten rules that everyone follows and nobody can enforce in court. Ministers resign when they lose the confidence of the Commons, the monarch grants Royal Assent to bills that have passed, and a government that loses a general election leaves office. None of that is required by any statute.

How Parliament is put together

Parliament has two houses, and the supreme legislative body is formally the Crown in Parliament, with unlimited powers of legislation subject only to convention.

The House of Commons has 650 members. Each represents one constituency and is elected by first-past-the-post, the candidate with most votes taking the seat regardless of whether they have a majority of those cast. Members hold office for up to five years and must then stand again. The system tends to convert a plurality of votes into a majority of seats, which is why the United Kingdom has produced single-party governments for most of the past century from parties that most voters did not choose.

The House of Lords is unelected. It was previously a largely hereditary aristocratic chamber including life peers and Lords Spiritual, the bishops of the established church, and it has been midway through extensive reform for decades, the most recent substantial change being the House of Lords Act 1999, which reduced the number of hereditary peers.

Bills normally become law when passed by both houses and presented for Royal Assent. The Parliament Acts provide a route past the Lords, so the upper house delays rather than blocks, and the Commons has the last word on anything it insists upon.

What the Crown still is

The monarch is head of state and takes little direct part in government, but the Crown remains the source from which ultimate power over the executive, the judiciary, the legislature and the established Church of England formally flows.

That formality is not decorative, because a great deal of executive power is still exercised as royal prerogative rather than under statute. Prerogative powers cover areas including the deployment of the armed forces, the conduct of foreign affairs and the appointment of ministers, and in practice they are exercised by ministers in the monarch's name. A power that has no statutory basis is also a power Parliament never granted and can be harder to scrutinise for exactly that reason.

The convention governing all of it is that the monarch acts on the advice of ministers. The reserve powers that would allow otherwise exist in theory and are not used, and the arrangement holds because everyone involved treats it as binding.

How a government is made and unmade

The executive is drawn from Parliament and answerable to it, as in other Westminster systems. The prime minister is the head of government and leads a cabinet of senior ministers whom they select, and His Majesty's Government is the principal instrument for public policymaking and the administration of public services.

There is no investiture vote of the kind continental parliaments hold. A government exists because it commands the confidence of the House of Commons, which is tested only when someone challenges it, and a successful vote of no confidence forces the government either to resign or to seek a parliamentary dissolution.

England has no separate government of its own. It is governed directly by the prime minister and the United Kingdom government, which is the asymmetry at the centre of the devolution settlement and the one nobody has resolved.

The permanent machinery sits underneath. Government departments are staffed by a professional civil service that continues across changes of administration, which is the institutional memory of a system in which ministers can change overnight and often do.

What devolution actually devolved

Parliament has devolved legislative powers to the parliaments of Scotland and Wales and to the assembly of Northern Ireland. Each has its own executive, headed by a first minister assisted by a deputy first minister and ministers with individual portfolios, and each controls a substantial budget: the Scottish Government's annual budget was almost £60 billion in the 2024 to 2025 financial year.

The settlements are not identical, and that is the point rather than an oversight. Scotland, Wales and Northern Ireland each received a different set of powers at a different time for a different reason, and the arrangements have been revised separately since. There is no general federal principle underneath them.

Devolution also sits inside parliamentary sovereignty rather than above it. The powers were granted by statute and could in principle be altered by statute, which distinguishes the arrangement from federalism, where the constituent units hold powers a central legislature cannot simply take back. Convention restrains that possibility; law does not.

Many other limited powers are granted by statute to the Privy Council, to ministers and to other authorities, to make delegated legislation on particular subjects. The volume of law made this way rather than by Parliament directly is one of the standing criticisms of the system.

What the party system has done with the rules

The United Kingdom is a multi-party system in which two parties have dominated since the 1920s, the Conservative Party and the Labour Party, with the Liberal Party occupying one of those positions before Labour displaced it. That displacement is the only complete turnover in the top two in a century, and it took two decades.

First-past-the-post is why. A party whose support is spread evenly across the country can win a substantial share of the national vote and almost no seats, while a party whose support is concentrated in particular constituencies converts votes into seats efficiently. The system rewards geography as much as popularity, and it has kept the two large parties in place while third parties rose and fell around them.

The nationalist parties are the exception that proves the mechanism. Support concentrated inside Scotland, Wales or Northern Ireland translates into seats at Westminster in a way that support spread thinly across England does not, so the parties that argue about the union are structurally advantaged at the parliament of the union.

The consequence for governing is that coalitions are rare and majorities are usual, and a government with a working majority in the Commons faces very few checks between elections. There is no written constitution to constrain it, no upper house that can block it and no court that can strike its legislation down. What restrains a British government is the next election and the conventions it chooses to observe.

Who interprets the law

The Constitutional Reform Act 2005 set out plans for a Supreme Court of the United Kingdom to replace the judicial role of the Law Lords, separating the highest court from the upper house of the legislature for the first time.

The change was institutional rather than constitutional in effect. The new court cannot strike down an Act of Parliament, because parliamentary sovereignty means there is no higher law against which to measure one. What it can do is interpret statute, rule on the limits of executive power, decide whether ministers have acted within the authority Parliament gave them, and determine questions about the devolution settlements.

That last function has grown. A system with three devolved legislatures and no written constitution generates disputes about who may legislate on what, and the court is where they are settled, which has made it a constitutional actor in a country that formally has no constitutional court.

Scotland retained its own legal system through the union of 1707 and still has it, so the United Kingdom contains distinct jurisdictions with different courts, different procedures and in some areas different law. A single state with three legal systems is another feature that follows from union rather than from design.

Where power sits below the nations

Local government in the United Kingdom is weaker relative to the centre than in most of western Europe, and it is organised differently in each of the four countries. England has a patchwork of unitary authorities, county and district councils, combined authorities and directly elected mayors, accumulated through successive reorganisations that never applied uniformly.

The financial position is the substance of the arrangement. Local authorities raise a limited share of what they spend and depend on transfers set centrally, and the services they deliver are largely statutory duties defined by Parliament rather than choices they make. A council that cannot set its own revenue is administering national policy locally rather than governing.

Scotland, Wales and Northern Ireland each run their own local government systems, answerable to the devolved administrations rather than to Westminster. That gives four separate arrangements inside one state, and it means a comparison of local services across the United Kingdom is a comparison of four policies rather than of four outcomes under one.

The English mayors are the recent development and the one worth watching. Directly elected mayors of city regions have acquired transport, housing and skills powers by negotiated deal rather than by general statute, which reproduces at city level the same asymmetry that devolution created at national level: powers granted case by case, held at the centre's discretion, and different in every place.

Where the country stands internationally

The United Kingdom joined the United Nations on 24 October 1945 as a founding member and holds a permanent seat on the Security Council. It joined NATO at its foundation on 4 April 1949, the Council of Europe on 5 May 1949, the Organisation for Economic Co-operation and Development in 1961, the G7 in 1977 and the G20 in 1999.

The change of the past decade is the departure from the European Union, decided by referendum in June 2016, notified under Article 50, and completed after the leaving date was extended more than once. The country is now outside the single market and the customs union, and the consequences run through trade, migration, regulation and the Northern Ireland border in particular.

That border is where the constitutional and the international meet. Northern Ireland's settlement rests on agreement between two governments and both communities, and it was reached when both states were inside the same economic arrangements. Managing a frontier between different regulatory regimes without a hard border on the island has been the hardest single consequence of departure. United Kingdom: economy covers what leaving did to trade and United Kingdom: history how the border came to be there.