In the 1st millennium BC the Celts overran the British Isles, as they did virtually all of western Europe. With iron ploughs they cultivated the heavy soil of the river valleys; with iron weapons and two-wheeled, horse-drawn chariots, they subdued and absorbed the indigenous inhabitants of the islands. Their priests, the Druids, dominated their society.

Romans:

Although it had long been known to the Mediterranean peoples as a source of tin, Great Britain did not enter the Roman world until Julius Caesar’s two expeditions to the island in 55 and 54 BC—as an afterthought to his conquest of Gaul. Caesar’s contact, however, was temporary; permanent occupation had to wait until Rome had solved more pressing problems at home.

Emperor Claudius I invaded Britain in force in AD 43, but nearly two decades passed before the Romans had captured the island of Anglesey, Wales, headquarters of the Druids, and put down the revolt of Boudicca, the queen of the Iceni. The Roman governor Gnaeus Julius Agricola won the Battle of Mons Graupius (AD 84), somewhere in Scotland, but the northern tribes proved hard to subdue. In 123, Hadrian’s Wall, stretching 117 km (73 mi) from the Solway Firth to the River Tyne, became the northern frontier.

Anglo-Saxons:

Collective name for the Germanic peoples who, in the 5th to 6th centuries AD, migrated to Britain from the North Sea coastlands between the Netherlands and Norway. They conquered and occupied lowland Britain, and the period of their dominance—the Anglo-Saxon period of British history—runs from the first half of the 5th century to the Norman Conquest of AD 1066.