A state with no founding document
The United Kingdom has no founding document and no single written constitution. The House of Commons Library describes a multi-national state that grew by stages over several centuries, and its rules live in statutes, court judgments and accepted practice. Even the full name, the United Kingdom of Great Britain and Northern Ireland, reads like the latest entry in a long ledger of agreements.
Wales came first. The English Crown annexed it in 1284, and Acts of 1535 and 1542 folded it into England and made English the language of the law. Welsh held on regardless: in the 2021 census, 538,000 people in Wales said they could speak it.
Scotland joined on very different terms. The two kingdoms came to share a monarch in 1603, yet they stayed separate states for another century. On 1 May 1707 a single Parliament of Great Britain replaced the two old ones. Scotland's Presbyterian church was guaranteed its status and the country held on to its own legal system, one reason the UK still has three separate jurisdictions.
The union with Ireland proved the most fragile. The Union with Ireland Act 1800 abolished the Irish parliament and merged the two kingdoms. After a long campaign for home rule and a war of independence, the Government of Ireland Act 1920 partitioned the island. The Irish Free State was proclaimed on 6 December 1922, and the next day Northern Ireland's parliament resolved to stay in the UK.
The result is a partnership of unequal size. In mid-2025 England held nearly 59 million of the UK's 69.5 million people, and Northern Ireland fewer than two million.
Coal, cotton and the Atlantic
Great Britain is where the Industrial Revolution began, around 1760 by the usual reckoning. Accessible coal and iron, good ports and canals, and available capital all helped. Textiles became the first industry to adopt modern methods, and Manchester's factories earned it the nickname Cottonopolis.
British merchants were also growing rich on the Atlantic. For a time Britain led the world in slave trading, and between 1640 and 1807 its ships carried about 3.4 million Africans across the ocean. Some 450,000 of them died on the crossing, while traders in London, Bristol and Liverpool took the profits. The trade became illegal on 1 May 1807, yet those already enslaved in the colonies stayed enslaved. A law of 1833 freed people in most British territories from the following year, but they had to go on working unpaid as apprentices, and full emancipation came only in 1838. The owners received £20 million in compensation, around 40 percent of government spending in 1833. The freed people received nothing, and the loan behind the payout was only finally repaid in 2015.
By 1920 the British Empire covered about 24 percent of the Earth's land, and its record was often grim. Potato blight reached Ireland, then fully part of the UK, in 1845, and in 1847 the cost of relief was pushed onto local taxation. Estimates of the dead run from around 800,000 to more than a million, and the population fell from 8.2 million in 1841 to 6.6 million in 1851. The end of British rule in India at midnight on 14 to 15 August 1947 brought partition, with ten million refugees and up to a million killed, according to the National Army Museum. For many, the handover of Hong Kong on 1 July 1997 marked the empire's close, though 14 Overseas Territories remain.
A union that keeps changing shape
Empire also changed Britain itself. The Empire Windrush docked at Tilbury on 21 June 1948 with 1,027 passengers, most of them from the Caribbean. By 2021 about one in six residents of England and Wales had been born outside the UK.
Northern Ireland's divisions turned violent. Unionists wanted to stay in the UK, while nationalists, mostly Catholic, wanted a united Ireland. A civil rights movement campaigned against discrimination in housing, jobs and voting, riots in August 1969 brought in British troops, and direct rule from London began in 1972. More than 3,500 people died, by the counts held at Ulster University's CAIN archive, though totals vary with method. The Belfast/Good Friday Agreement of 10 April 1998, approved by voters on 22 May, rests on the principle of consent for Northern Ireland's status. Its devolved institutions stalled in 2017 to 2020 and in 2022 to 2024.
Scotland and Wales voted for devolution in 1997, the Welsh by just 6,721 votes, and a new Scottish Parliament first met on 12 May 1999. In 2014 voters in Scotland rejected independence by 55.3 percent to 44.7. Two years later the UK voted by 51.9 percent to leave the European Union, though Scotland backed Remain with 62 percent and Northern Ireland with 55.8. Membership ended on 31 January 2020, and Northern Ireland stays within the EU's single market for goods.
The old foundations keep shifting. Ratcliffe-on-Soar, the UK's last coal-fired power station, closed on 30 September 2024. Coal had generated Britain's electricity for 142 years and fed its industry for far longer. The Cabinet Manual says the constitutional order is still evolving, a line that would serve as well as any for the country itself.
