In late Roman times Brough seems to have lost its original importance as a military centre and to have been replaced by Malton further to the north. Malton supplied the line of coastal signal stations that probably stretched from Flamborough Head to the Tees .
It has been speculated that Germanic laeti settled in this military zone had little contact with civilian authorities. When Roman military command chain ceased to function they had little difficulty in cutting loose from whatever post Roman territorial authority emerged, to found a barbarian kingdom.
The first settlers then must have come, perhaps as laeti, from this region and in particular from the district around Borgstedt. The pottery found at Sancton also shows in addition to this strong Anglian derivation, links to the Saxon cemeteries around the mouth of the Elbe, to Alemmanic peoples and to the Franks. All these groups were probably introduced under Roman control. There are strong hints at continuous occupation at York from late Roman times into the Dark Ages.
From York, Deiran settlement spread north perhaps as far as Catterick. Beyond this, Roman civil administration seems to have been absent and it is on a Celtic society that the kingdom of Bernicia was founded.