I’ve recently become interested in the sub-Roman period of Britain and have found it striking that it appears the British managed to hold off the encroaching Angles & Saxons until well into the 6th century when it suddenly appears that there is an acceleration of Anglo-Saxon culture. How much of this is down to the Plague of Justinian (if it is even relevant), and the fact that it seems like the native Brits/Romano-British were more likely to cluster together in larger groups/towns & cities?