Four nations in one state

The United Kingdom of Great Britain and Northern Ireland is, as its name implies, a union of several components: the kingdom of England, the kingdom of Scotland, the principality of Wales, and the province of Northern Ireland. There are different patterns of culture, identity and political allegiance within and between each of these components.

England is the largest, richest and most powerful of the four components, and the institutional core of the United Kingdom (London being the capital of the U.K., as well as by far its largest city).

A united Kingdom of England was created in the tenth century, with Edgar I (959-975) crowned king of all England in 973. It was subsumed into the United Kingdom of Great Britain by the Act of Union with Scotland in 1707.

Wales was united to England by a long process of conquest and partial colonization, culminating in the 1536 "Acte for Lawes & Justice to be ministred in Wales in like fourme as it is in this Realme", which formally incorporated Wales into the same structures of law and government as England.

Scotland was an entirely separate kingdom, which successfully withstood English attempts at conquest in the 14th century. England and Scotland shared a monarch from 1603 onwards, when James VI of Scotland became James I of England, and assumed the courtesy title "King of Britain". Formal unification of England and Scotland under a single crown and parliament, with a curency and customs union and freedom of movement between the two kingdoms, was agreed by the parliaments of Scotland and England, and legislated in the Act of Union with Scotland 1707.

Kings of England claimed lordship over Ireland from 1171 onwards, but English rule in Ireland was seldom effective or widely heeded before Henry VIII declared himself King of Ireland in 1535, initiating more intensive efforts to enforce the royal will there. Ireland was fully incorporated into the United Kingdom by the Act of Union with Ireland 1801, but 26 of the 32 counties left the Union in 1921 to form the Irish Free State (which became the Republic of Ireland in 1949). The 6 counties where the majority of the population wished to remain part of the United Kingdom became Northern Ireland.