The 400-year period following the collapse of Roman rule is the most difficult to interpret in the history of Wales. After the Roman departure in AD 410, much of the lowlands of Britain to the east and south-east was overrun by various Germanic peoples, commonly known as Anglo-Saxons. Some have theorized that the cultural dominance of the Anglo-Saxons was due to apartheid-like social conditions in which the Britons were at a disadvantage.