[3] After the Norman conquest of England in the 11th century, William de Mohun constructed a timber castle on the site as part of the pacification of Somerset.

[3][6] The prosperity of Dunster was based on the wool trade, with profits helping to pay for the construction of the tower of the Priory Church of St George and provide other amenities.

They carried out restoration works, however this was controversial as the shape of the roof was changed to more closely resemble the appearance of the original building, rather than that produced by subsequent revisions.

[10] The octagonal building, which is 9.4 metres (31 ft) in diameter, has a central stone pier which supports a heavy timber framework for the structure.

[2] One of the roof beams has a hole in it, a result of cannon fire in the Civil War, when Dunster Castle was a besieged Royalist stronghold for five months under the command of Colonel Wyndham.

[2] The building was the inspiration for the Rest House, on Bournville Village Green in Birmingham, which was built in 1914 to commemorate the silver wedding anniversary of Mr and Mrs George Cadbury.