Umbrella Brittonic-speaking Celtic population of Great Britain south of the Forth-Clyde line before and during the Roman period, organized in numerous separate tribal kingdoms (Iceni, Brigantes, Catuvellauni, and others) rather than a single state.
Gradually Romanized under provincial rule (43-410 CE); after Rome's withdrawal, Brittonic identity persisted in western/northern Britain (ancestral to the Welsh, Cornish, and Cumbric-speaking kingdoms) while eastern Britain was progressively taken by incoming Anglo-Saxons.
Standard modern survey covering the Britons from the Iron Age through the Roman period and into the early medieval successor kingdoms.