The name "Britain" comes from the word "Pretani", the Greco-Roman word for the inhabitants of Britain. The Romans mispronounced the word and called the island "Britannia".
The Romans had invaded because the Celts of Britain were working with the Celts of Gaul (France) against them. The British Celts were giving them food, and allowing them to hide in Britain. There was another reason. The Celts used cattle to pull their ploughs and this meant that richer, heavier land could be farmed. Under the Celts Britain had become an important food producer because of its mild climate. It now exported corn and animals, as well as hunting dogs and slaves, to the European mainland. The Romans could make use of British food for their own army fighting the Gauls (French).
The Romans brought the skills of reading and writing to Britain. The written word was important for spreading ideas and also for establishing power. As early as ad 80 the governor Agricola "trained the sons of chiefs in the liberal arts . . . the result was that the people who used to reject Latin began to use it in speech and writing. Further the wearing of our national dress came to be valued and the toga [the Roman cloak] came into fashion." While the Celtic peasantry remained illiterate and only Celtic-speaking, a number of town dwellers spoke Latin and Greek with ease, and the richer landowners in the country almost certainly used Latin. But Latin completely disappeared both in its spoken and written forms when the Anglo-Saxons invaded Britain in the fifth century ad. Britain was probably more literate under the Romans than it was to be again until the fifteenth century.
Julius Caesar first came to Britain in 55 bc, but it was not until almost a century later, in ad 43, that a Roman army actually occupied Britain. The Romans were determined to conquer the whole island. They had little difficulty because they had a better trained army and because the Celtic tribes fought among themselves.
The Romans established a Romano-British culture across the southern half of Britain, from the River Humber to the River Severn. This part of Britain was inside the empire. Beyond were the upland areas, under Roman control but not developed.
The total Roman army in Britain was about 40,000 men. The Romans could not conquer "Caledonia", as they called Scotland, although they spent over a century trying to do so. At last they built a strong wall along the northern border, named after the Emperor Hadrian who planned it. At the time, Hadrian's wall was simply intended to keep out raiders from the north. But it also marked the border between the two later countries, England and Scotland.
Roman control of Britain came to an end as the empire began to collapse. The first signs were the attacks by Celts of Caledonia in ad 367. The Roman legions found it more and more difficult to stop the raiders from crossing Hadrian's wall. The same was happening on the European mainland as
Germanic groups, Saxons and Franks, began to raid the coast of Gaul (France). In ad 409 Rome pulled its last soldiers out of Britain and the Romano-British, the Romanised Celts, were left to fight alone against the Scots, the Irish and Saxon raiders from Germany. The following year Rome itself fell to raiders. When Britain called to Rome for help against the raiders from Saxon Germany in the mid-fifth century, no answer came.