The 360s were a decade of unrest in Roman Britain, as the province came under repeated attack by its barbarian neighbours: Scotti and Attacotti from Ireland, Saxons from the Continent, and Picts from Caledonia. In AD 367, a high-ranking officer named Fullofaudes was caught in an ambush and killed; he was probably none other than the dux Britanniarum (“Duke of the British provinces”), who commanded all of the army units along Hadrian’s Wall and its hinterland. The emperor Valentinian was finally obliged to send Count Theodosius, a veteran commander, to combat what Ammianus Marcellinus characterized as a barbarica conspiratio (colourfully rendered as “a conspiracy of the savages” by one translator). By AD 369, Theodosius had restored order, reportedly crushing roving bands of raiders, routing entire tribes, and relieving beleaguered towns.
In the course of these events, according to Ammianus, “a fearful development took place, which would have resulted in grave danger if it had not been crushed at the outset” ( 28.3.3). This was the “heinous plot” of a would-be usurper, nipped in the bud by Theodosius, who condemned the conspirators to death and restored the province to its former state. As one of his measures, he allegedly “removed from their posts the , a class of men established long ago, who had gradually fallen into evil ways” ( 28.3.8). Ammianus writes that “it had been their
