This vision of the Anglo-Saxons exercising extensive political and military power at an early date remains contested. The most developed vision of a continuation in sub-Roman Britain, with control over its own political and military destiny for well over a century, is that of Kenneth Dark, who suggests that the sub-Roman elite survived in culture, politics and military power up to c. 570. Bede, however, identifies three phases of settlement: an exploration phase, when mercenaries came to protect the resident population; a migration phase, which was substantial as implied by the statement that "Anglus" was deserted; and an establishment phase, in which Anglo-Saxons started to control areas, implied in Bede's statement about the origins of the tribes.