Dunster Castle 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
Feudal barony of Dunster War he made Dunster Castle available for use as a convalescent home by the Royal Navy. On the death of his father in 1944 the payment of a large sum in Death Duties left the estate indebted and uneconomic to operate, and Geoffrey, whilst reserving a tenancy for himself at the Castle, sold the estates to a property development company which sold them on to the Commissioners of Crown Lands. He bought back the Castle and grounds in 1954 and opened them to the paying public. He died in 1957 and his widow remained at the Castle until her death