[3] The mound measures 30 metres (98 ft) across the top, and may have exploited an existing Viking site.

[4] Recent academic work has suggested that the castle was built around 1100, after the surrounding region of Somerset had become stable in the years following the Norman invasion of England and the subsequent Anglo-Saxon rebellion against Norman rule.

[5] The location Down End was strategically well placed, as the nearby Parrett is an important tidal river, essential for trade during the early medieval period.

[6] The de Columbers were probably responsible for building the castle, which also enjoyed a good defensive position on a natural ridge, protected by several nearby streams; the family also built nearby Stowey Castle.

[7][nb 1] Down End became a new borough town in 1225, but may have existed as a settlement and port from 1159 onwards; the de Columbers were lords of the manor of nearby Puriton in the late 12th century.