Almost everyone in Britannia was legally and culturally 'Roman' The Roman conquest, which started in AD 43, illustrates the profound cultural and political impact that small numbers of people can have in some circumstances, for the Romans did not colonise the islands of Britain to any significant degree. To a population of around three million, their army, administration and carpet-baggers added only a few per cent.
'The future Scotland remained beyond Roman government, although the nearby presence of the empire had major effects.'
The province's towns and villas were overwhelmingly built by indigenous people - again the wealthy - adopting the new international culture of power. Greco-Roman civilisation displaced the 'Celtic' culture of Iron Age Europe. These islanders actually became Romans, both culturally and legally (the Roman citizenship was more a political status than an ethnic identity). By AD 300, almost everyone in 'Britannia' was Roman, legally and culturally, even though of indigenous descent and still mostly speaking 'Celtic' dialects. Roman rule saw profound cultural change, but emphatically without any mass migration.
However, Rome only ever conquered half the island. The future Scotland remained beyond Roman government, although the nearby presence of the empire had major effects. The kingdom of the Picts appeared during the third century AD, the first of a series of statelets which, during the last years and collapse of Roman power, developed through the merging of the 'tribes' of earlier times.
Were the 'Celts' displaced or absorbed by the invaders? In western and northern Britain, around the western seas, the end of Roman power saw the reassertion of ancient patterns, ie continuity of linguistic and cultural trends reaching back to before the Iron Age. Yet in the long term, the continuous development of a shifting mosaic of societies gradually tended (as elsewhere in Europe) towards larger states. Thus, for example, the far north-western, Irish-ruled kingdom of Dalriada merged in the ninth century with the Pictish kingdom to form Scotland.
'It was once believed that the Romano-British were slaughtered or driven west by hordes of invading Anglo-Saxons, part of the great westward movement of 'barbarians' overwhelming the western empire.'
The western-most parts of the old province, where Roman ways had not displaced traditional culture, also partook of these trends, creating small kingdoms which would develop, under pressure from the Saxons, into the Welsh and Cornish regions.
The fate of the rest of the Roman province was very different: after imperial power collapsed c.410 AD Romanised civilisation swiftly vanished. By the sixth century, most of Britannia was taken over by 'Germanic' kingdoms. There was apparently complete discontinuity between Roman Britain and Anglo-Saxon England; it was once believed that the Romano-British were slaughtered or driven west by hordes of invading Anglo-Saxons, part of the great westward movement of 'barbarians' overwhelming the western empire. However, there was no such simple displacement of 'Celts' by 'Germans'.