Thetford Castle

The site is dominated by a very large artificial mound set within surrounding ditches and an attached rectangular enclosure. The surviving earthworks combine the man-made motte, an outer ditch, a series of ramparts on the north side and a bailey that exploits older defences, giving the layout a layered appearance that incorporates earlier prehistoric and Saxon features.

The motte is the principal feature, standing about 19.6 metres tall from its summit (measuring about 22 metres from the base of the surrounding ditch) and roughly 100 metres across at the base. It was formed from local chalk dug and moved by hand, with workers using wooden shovels in a process estimated to have required about 24,000 man-days. The motte sits within a deep encircling ditch and on its north side was defended by two sets of complex ramparts that probably reused elements of an earlier Iron Age fortification. After the deliberate dismantling of the castle defences in 1173 the mound remained essentially intact, and it survives today within a public park as a protected scheduled monument.

The bailey lies beside the motte as a roughly rectangular enclosure, approximately 105 metres by 95 metres, and one side was laid out to take advantage of pre-existing Iron Age earthworks. The bailey’s banks were built from the same local chalk as the motte; tradition records that additional material was quarried from a nearby area known as the Gallows Pits because the ditch material alone was insufficient. In the 12th century a stone wall was likely erected around the bailey and there is also a suggestion that a stone keep may have been built. The east bank of the outer bailey was removed in 1772, and the bailey area today is known as Military Parade.

Evidence for the earlier fort, Red Castle, survives in the form of a ringwork aligned across a Saxon ditch, a layout that enclosed the churchyard and overbuilt part of the cemetery. Excavations in the mid-twentieth century clarified the form and dating of this 11th-century ringwork, confirming its sequence before the larger motte-and-bailey replaced it. Local commentary over the centuries has preserved folklore about the mound’s creation alongside the archaeological picture of Norman construction and later modification.