Parliament of the United Kingdom in the context of "Constituencies of the Parliament of the United Kingdom"

The constitution of the United Kingdom comprises the written and unwritten arrangements that establish the United Kingdom of Great Britain and Northern Ireland as a political body. Unlike in most countries, no official attempt has been made to codify such arrangements into a single document, thus it is known as an uncodified constitution. This enables the constitution to be easily changed as no provisions are formally entrenched.

The Supreme Court of the United Kingdom and its predecessor, the Appellate Committee of the House of Lords, have recognised and affirmed constitutional principles such as parliamentary sovereignty, the rule of law, democracy, and upholding international law. It also recognises that some Acts of Parliament have special constitutional status. These include the Magna Carta, which in 1215 required the King to call a "common counsel" (now called Parliament) to represent the people, to hold courts in a fixed place, to guarantee fair trials, to guarantee free movement of people, to free the church from the state, and to guarantee rights of "common" people to use the land. After the Glorious Revolution, the Bill of Rights 1689 and the Claim of Right Act 1689 cemented Parliament's position as the supreme law-making body, and said that the "election of members of Parliament ought to be free". The Treaty of Union in 1706 and the Acts of Union 1707 united the Kingdoms of England, Wales and Scotland, the Acts of Union 1800 joined Ireland, but the Irish Free State separated after the Anglo-Irish Treaty in 1922, leaving Northern Ireland within the UK. After struggles for universal suffrage, the UK guaranteed every adult citizen over 21 years the equal right to vote in the Representation of the People (Equal Franchise) Act 1928. After World War II, the UK became a founding member of the Council of Europe to uphold human rights, and the United Nations to guarantee international peace and security. The UK was a member of the European Union, joining its predecessor in 1973, but left in 2020. The UK is also a founding member of the International Labour Organization and the World Trade Organization to participate in regulating the global economy.

The Brexit withdrawal agreement, officially titled Agreement on the withdrawal of the United Kingdom of Great Britain and Northern Ireland from the European Union and the European Atomic Energy Community, is a treaty between the European Union (EU), Euratom, and the United Kingdom (UK), signed on 24 January 2020, setting the terms of the withdrawal of the UK from the EU and Euratom. The text of the treaty was published on 17 October 2019, and is a renegotiated version of an agreement published in November 2018. The earlier version of the withdrawal agreement was rejected by the House of Commons on three occasions, leading to the resignation of Theresa May as Prime Minister and the appointment of Boris Johnson as the new prime minister on 24 July 2019.

The Parliament of the United Kingdom gave its approval to the agreement on 23 January 2020 and the UK government deposited Britain's instrument of ratification on 29 January 2020. The agreement was ratified by the Council of the European Union on 30 January 2020, following the consent of the European Parliament on 29 January 2020. The United Kingdom's withdrawal from the Union took effect on 11 p.m. GMT on 31 January 2020, and at that moment the Withdrawal Agreement entered into force, as per its article 185.

London is the capital and largest city of both England and the United Kingdom, with a population of 9.1 million people in 2024. Its wider metropolitan area is the largest in Western Europe, with a population of 15.1 million. London stands on the River Thames in southeast England, at the head of a 50-mile (80 km) tidal estuary down to the North Sea, and has been a major settlement for nearly 2,000 years. Its ancient core and financial centre, the City of London, was founded by the Romans as Londinium and has retained its medieval boundaries. The City of Westminster, to the west of the City of London, has been the centuries-long host of the national government and parliament. London grew rapidly in the 19th century, becoming the world's largest city at the time. Since the 19th century the name "London" has referred to the metropolis around the City of London, historically split between the counties of Middlesex, Essex, Surrey, Kent and Hertfordshire, which since 1965 has largely comprised the administrative area of Greater London, governed by 33 local authorities and the Greater London Authority.

As one of the world's major global cities, London exerts a strong influence on world art, entertainment, fashion, commerce, finance, education, healthcare, media, science, technology, tourism, transport and communications. London is Europe's largest city economy and one of the world's major financial centres. London hosts Europe's largest concentration of higher education institutions, comprising over 50 universities and colleges and enrolling more than 500,000 students as at 2023. It is home to several of the world's leading academic institutions: Imperial College London, internationally recognised for its excellence in natural and applied sciences, and University College London (UCL), a comprehensive research-intensive university, consistently rank among the top ten globally. Other notable institutions include King's College London (KCL), highly regarded in law, humanities and health sciences; the London School of Economics (LSE), globally prominent in social sciences and economics; and specialised institutions such as the Royal College of Art (RCA), Royal Academy of Music (RAM), the Royal Academy of Dramatic Art (RADA), the School of Oriental and African Studies (SOAS) and London Business School (LBS). It is the most-visited city in Europe and has the world's busiest city airport system. The London Underground is the world's oldest rapid transit system.

Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the second-largest country by total area, with the longest coastline of any country. Its border with the United States is the longest international land border. The country is characterized by a wide range of both meteorologic and geological regions. With a population of over 41 million, it has widely varying population densities, with the majority residing in its urban areas and large areas being sparsely populated. Canada's capital is Ottawa and its three largest metropolitan areas are Toronto, Montreal, and Vancouver.

Indigenous peoples have continuously inhabited what is now Canada for thousands of years. Beginning in the 16th century, British and French expeditions explored and later settled along the Atlantic coast. As a consequence of various armed conflicts, France ceded nearly all of its colonies in North America in 1763. In 1867, with the union of three British North American colonies through Confederation, Canada was formed as a federal dominion of four provinces. This began an accretion of provinces and territories resulting in the displacement of Indigenous populations, and a process of increasing autonomy from the United Kingdom. This increased sovereignty was highlighted by the Statute of Westminster, 1931, and culminated in the Canada Act 1982, which severed the vestiges of legal dependence on the Parliament of the United Kingdom.

The Westminster system, or Westminster model, is a type of parliamentary government modelled on that of the Parliament of the United Kingdom. Key aspects of the system include an executive branch made up of members of the legislature which is responsible to the legislature; the presence of parliamentary opposition parties; and a ceremonial head of state who is separate from the head of government. The term derives from the Palace of Westminster, the seat of the British parliament. The Westminster system can be contrasted with the presidential system, which originated in the United States, and with the semi-presidential system based on the government of France.

The Westminster system is used, or was once used, in the national and subnational legislatures of most former colonies of the British Empire upon gaining self-government, beginning with the Province of Canada in 1848. However, many former colonies have since adopted other forms of government.

A legislature (UK: /ˈlɛdʒɪslətʃər/, US: /-ˌleɪtʃər/) is a deliberative assembly that holds the legal authority to make law and exercise political oversight within a political entity such as a state, nation, or city. Legislatures are among the principal institutions of state, typically contrasted with the executive and judicial institutions. They may exist at different levels of governance—national, subnational (state, provincial, or regional), local, or supranational—such as the European Parliament.

In most political systems, the laws enacted by legislatures are referred to as primary legislation. Legislatures may also perform oversight, budgetary, and representative functions. Members of a legislature, called legislators, may be elected, indirectly chosen, or appointed, and legislatures may be unicameral, bicameral, or multicameral, depending on their constitutional design.

The Constitution Act, 1867 (French: Loi constitutionnelle de 1867), originally enacted as the British North America Act, 1867 (BNA Act), is a major part of the Constitution of Canada. The act created Canada, a federal country, and defines much of its structure, including the Parliament of Canada (composed of the monarch, the House of Commons, and the Senate), the executive, parts of the court system, and the division of powers between the federal government and the provinces. The act also created two new provinces, Ontario and Quebec, and set out their constitutions.

In 1982, with the patriation of the Constitution, the British North America Acts which were originally enacted by the British Parliament, including this act, were renamed the Constitution Acts. However, the acts are still known by their original names in records of the United Kingdom. Amendments were also made at this time: section 92A was added, giving provinces greater control over non-renewable natural resources.

The British North America Acts, 1867–1975, are a series of acts of Parliament that were at the core of the Constitution of Canada. Most were enacted by the Parliament of the United Kingdom and some by the Parliament of Canada. Some of the acts were repealed in Canada by the Constitution Act, 1982. The rest were renamed the Constitution Acts and amended, with those changes having effect only in Canada. The Canadian versions of the Constitution Acts are part of the Constitution of Canada, and can be amended only in Canada.

The British versions of the acts which remain in force in Britain are ordinary British statutes. They can be amended by the British Parliament, but those amendments would not have any effect in Canada. They retain their original names and do not include any amendments made after 1964.

Before 1982, modifying the Constitution of Canada primarily meant amending the British North America Act, 1867. Unlike most other constitutions, however, the Act had no amending formula; instead, changes were enacted through Acts of the Parliament of the United Kingdom (or "Imperial Parliament") called the British North America Acts.

Other Commonwealth countries had taken over the authority for constitutional amendment after the Statute of Westminster 1931, but at the time, Canada decided to allow the Parliament of the United Kingdom to retain the power "temporarily". Between 1931 and 1982, the federal government, on behalf of the House of Commons of Canada and the Senate, would issue an address to the British government requesting an amendment. The request would include a resolution containing the desired amendments, which in turn were always passed by the British Parliament with little or no debate.