By the 8th century, the expanding power of Mercia led to conflict with the Welsh and by the beginning of the 9th century the western Mercians, who became known as the sub-kingdom of Magonset, had gained control over the area and nearby Hereford. During the rest of the century they moved its frontier southward to the banks of the Dore, the Worm Brook and a stream then known as the Taratur, annexing northern Ergyng. The sites of old British churches fell to Mercia, and the Britons became regarded as foreigners – or, in the Old English language, "Welsh" – in what had been their own land. The rump of Ergyng then became known to the English as Arcenefelde or Archenfield. There is no evidence that Offa built his famous Dyke across the area, probably because it had already been assimilated into Mercia by the late 8th century.