Provincia Britannia, today known as Roman Britain, was a province of the Roman Empire from 43 to 409, spanning at its height in 160, the southern three-quarters of the island of Great Britain.
Before the Roman invasion began in 43 AD, Iron Age Britain had already established cultural and economic links with continental Europe, but the Roman invaders introduced new developments in agriculture, urbanisation, industry and architecture. Beyond the first few decades after the initial invasion, Roman historians generally mention Britannia only in passing. Thus, most knowledge of Roman Britain has derived from archaeological investigations, and the epigraphic evidence lauding the Britannic achievements of an Emperor of Rome, such as Hadrian and Antoninus Pius , whose walls demarcated the northern borders of Roman Britain.
Julius Caesar conducted the first Roman campaigns in Britain in 55 and in 54 BC. The conquest did not begin until AD 43, in the reign of the Emperor Claudius. Following the conquest of the native Britons, a distinctive Romano-British culture emerged under provincial government, which, despite steadily extended territorial control northwards, was never able to exert definite control over Caledonia. The Romans demarcated the northern border of Britannia with Hadrian's Wall, completed around the year 128. Fourteen years later, in 142, the Romans extended the Britannic frontier northwards, to the Forth-Clyde line, where they constructed the Antonine Wall, but, after approximately twenty years, they then retreated to the border of Hadrian's Wall. Around the year 197, Rome divided Britannia into two provinces, Britannia Superior and Britannia Inferior; sometime after 305, Britannia was further divided, and made into an imperial diocese. For much of the later period of the Roman occupation, Britannia was subject to barbarian invasions and often came under the control of imperial usurpers and pretenders to the Roman Emperorship.
Roman officials departed from Britain around the year 410, which began the sub-Roman period (5thâ€“6th centuries), but the legacy of the Roman Empire was felt for centuries in Britain.