Hill, but the earliest evidence of a fortification at Dunster was an Anglo-Saxon burgh.<ref>Black Ball Camp, Arts and Humanities Data Service, accessed 28 September 2007; univallate Hillfort, Arts and Humanities Data Service, accessed 28 September 2007; Gathercole, ClareAn archaeological assessment of Dunster (PDF) Somerset County Council accessed 1 October 2011</ref> This was built on the summit of the hill and was possibly intended to protect the region against sea-borne raiders; by the mid-11th century it was controlled by a local nobleman called Aelfric. In 1066 the Normans invaded south-east England, defeating the English forces at the battle of Hastings: in the aftermath of the victory, William the Conqueror entrusted the conquest of the south-west of England to his half-brother Robert of Mortain. Expecting stiff resistance, Robert marched west into Somerset, supported by forces under Walter of Douai, who entered from the north; a third force, under the command of William de Mohun, landed by sea along the Somerset coast. William had been granted 68 manors in the region and by 1086 had established a castle at Dunster; this would form both the caput, or principal castle, for his new lands, and help guard the coast against the threat of any fresh sea-borne attack, as well as controlling the coastal road running from Somerset to Gloucestershire. This first castle was a motte and bailey design, built upon the former Anglo-Saxon burgh; the top of the Tor was scarped to form the motte, or Upper Ward, and an area below shaped to form the bailey, or Lower Ward. Somerset became more stable in the aftermath of the post-invasion period and the unsuccessful 1068 rebellion against Norman rule. It was common in the period for the Normans to build religious houses to accompany major castles, and accordingly William de Mohun endowed a Benedictine priory at Dunster in 1090, along with its parent abbey at Bath. The River Avill was important for trade; the region around Dunster was rich with fisheries and vineyards, and Dunster Castle prospered. Stone fortifications were built on the site during the early 12th century, probably forming a shell keep around the top of the motte. In the late 1130s England began to descend into a period of civil war known as the Anarchy, during which the supporters of King Stephen fought with those of the Empress Matilda for control of the kingdom. William de Mohun's eldest son, also called