History of the constitution of the United Kingdom

The constitution of the United Kingdom is an uncodified constitution made up of various statutes, judicial precedents, convention, treaties and other sources.^[1] Beginning in the Middle Ages, the constitution developed gradually in response to various crises. By the 20th century, the British monarchy had become a constitutional and ceremonial monarchy, and Parliament developed into a representative body exercising parliamentary sovereignty.^[2]

Initially, the constitutional systems of the four constituent countries of the United Kingdom developed separately under English domination. The Kingdom of England conquered Wales in 1283, but it was only later through the Laws in Wales Acts 1535 and 1542 that the country was brought completely under English law. While technically a separate state, the Kingdom of Ireland was ruled by the English monarchy.

From 1603 to 1707, England and the Kingdom of Scotland shared the same monarch as part of the Union of the Crowns; however, each nation maintained separate governments. In 1707, England and Scotland were joined in the Kingdom of Great Britain. In 1801, Great Britain and Ireland were joined in the United Kingdom of Great Britain and Ireland. While the United Kingdom remains a unitary state in which Parliament is sovereign, a process of devolution began in the 20th and 21st centuries that saw Parliament restore self-government to Scotland, Wales and Northern Ireland.

Aspects of the British constitution were adopted in the constitutions and legal systems of other countries around the world, particularly those that were part of, or formerly part of, the British Empire including the United States and those countries that adopted the Westminster parliamentary system. The British constitution is the source of the modern concepts of the rule of law, parliamentary sovereignty and judicial independence and adoption of British constitutional principles propagated their spread around the world. One of the oldest constitutional systems in the world, dating back over one thousand years, it is characterised by the stability of its governing institutions, its capacity to absorb change, a bicameral legislature and the concept of responsible government.