The expression Roman Britain may refer either to the period during which the island of Britain was part of the Roman Empire – i.e., the period from the middle of the first century CE to the first years of the fifth century CE – or to those regions of Britain which came under Roman authority – the south and east of the country were the first to be conquered, and for the greater part of the Roman occupation Hadrian’s Wall, running from the mouth of the River Tyne in the east to the Solway Firth in the west, marked the northern limit of Roman rule in Britain.
In the course of his campaigns to conquer Gaul (roughly modern France) the Roman general and politician Julius Caesar (101-44 BCE) invaded Britain twice, in 55 and 54 BCE, in part to punish the British tribes which had given help to the tribes he had been fighting in Gaul. However, he did not establish a permanent Roman presence in the country. Invasions planned by the emperors Augustus (reigned 27 BCE-14 CE) and Caligula (reigned 37-41 CE) never took take place, and it was not until 43 CE that a Roman army, under the command of the emperor Claudius (reigned 41-54 CE), again invaded Britain. Within a few years the Romans had secured control of the south and east of the country, though in 61 they had to deal with a rebellion led by Boudicca (Boadicea), queen of the Iceni (a tribe inhabiting Norfolk, parts of Suffolk, and Cambridgeshire). Some two decades later, Julius Agricola (40-93, governor of Britain 78-85) extended Roman rule into north Wales, northern England and the southern part of Scotland, and in his final campaign even took his army into the Scottish Highlands. (A (perhaps oversympathetic) account of his governorship may be found in De vita Iulii Agricolae (On the Life of Julius Agricola), the biography written by his son-in-law, the historian Tacitus.) In the years following Agricola’s governorship the Romans adopted a more defensive policy, and in 122 the emperor Hadrian (reigned 117-138), visiting Britain on a tour of inspection, ordered the construction of the wall which still bears his name. (Some historians believe that in 117 or a little later the Romans had suffered a military disaster involving the loss of an entire legion (the IX Legio Hispana), and that this event was responsible for the change of policy. For a little more see The Eagle of the Ninth.) Though hostile Scottish tribes prompted the Romans to undertake further campaigns in Scotland far north of Hadrian’s Wall, and in the second century the emperor Antoninus Pius (reigned 138-161 CE) decided to build a wall (the Antonine Wall) across the Scottish lowlands from the River Clyde to the Firth of Forth, Hadrian’s Wall, running from the mouth of the River Tyne to the Solway Firth, became effectively the northern frontier of the Roman Empire in Britain.
The Roman conquest of Britain not only paved the way for increased trade with other parts of the Empire but benefited the country economically in other ways. The Romans constructed roads, initially to facilitate the movement of troops – e.g., Watling Street (from London to Chester) and the Fosse Way (from Exeter to Lincoln) - and built towns which had administrative functions and served as commercial centres – e.g., London (Londinium), St. Albans (Verulamium), Bath (Aquae Sulis), Chester (Deva Victrix). Many of these towns were the site of permanent military encampments – a fact to which the town’s modern name bears witness: the endings –chester (as in Dorchester, Winchester), -cester (as in Cirencester, Bicester), and -caster (as in Doncaster, Tadcaster) derive from the Latin castra (camp). Amongst these foundations were four coloniae, i.e., settlements for retired soldiers who did not wish to return to their countries of origin - Colchester (Camulodunum), Gloucester (Glevum), Lincoln (Lindum), and York (Eburacum). It was primarily in the towns that Roman culture established itself, rural areas remaining largely unaffected.
In the third and fourth centuries, as the Roman Empire found itself under threat in many of its frontier provinces, the Roman armies garrisoned in Britain and serving to maintain Roman authority there were increasingly redeployed for service elsewhere in the Empire. At the same time Britain itself was subject to attacks, e.g., by Saxon invaders on its east and south coasts, and against these attacks the Romans were less and less able to provide any protection. By 410 – the year in which the Visigoths under Alaric captured the city of Rome – the Romans had virtually abandoned Britain.