The Roman invasion of Britain in 55 BC and most of Britain's consequent incorporation into the Roman Empire stimulated development and brought more active contacts with the rest of Europe. As Rome's strength declined, the nation again was exposed to invasion--including the pivotal incursions of the Angles, Saxons, and Jutes in the fifth and sixth centuries AD--up to the Norman conquest in 1066. Norman rule effectively ensured Britain's safety from further intrusions; certain institutions, which remain characteristic of Britain, could develop. Among these are a political, administrative, cultural, and economic center in London; a separate but accomplished church; a system of common law; typical and distinguished university education; and representative government.

Both Wales and Scotland were independent kingdoms that resisted English rule. The English conquest of Wales succeeded in 1282 under Edward I, and the Statute of Rhuddlan accomplished English rule 2 years later. To appease the Welsh, Edward's son , who had been born in Wales, was made Prince of Wales in 1301. The tradition of bestowing this title on the eldest son of the British Monarch continues today. An act of 1536 completed the political and administrative union of England and Wales.

Although often marked by economic and political nationalism, the Commonwealth offers the United Kingdom a voice in matters concerning many developing countries. In addition, the Commonwealth helps preserve many institutions deriving from British experience and models, such as parliamentary democracy, in those countries.