Wareham Castle was built in the south-west corner of the old Anglo-Saxon earthworks, taking the form of a motte with an inner and
outer bailey, protected with timber defences and a ditch. The original size of the motte is not known; 18th- and 19th-century records suggest it was between across. It is uncertain when the castle was built; it may have been constructed soon after the
Norman Conquest in 1066, although no physical evidence has been found to prove this theory. If the castle was built soon after 1066, the construction work may have required the extensive demolition of houses in that part of the town, and the decision to place it in the south-west sector may have been linked to the presence of a former Anglo-Saxon royal residence there. Robert Beaumont controlled the castle in 1118, when he passed it onto Robert, Earl of Gloucester, who carried out work on it in 1137. A small, square keep across with
pilaster buttresses at the corners, was built from stone rubble on the top of the motte, probably at the beginning of the 12th century. The bailey was protected by a stone curtain wall, known to have been thick in places. During the civil conflict known as
The Anarchy in the 1140s, Wareham Castle lay on the border between the territories of the rival claimants for the throne,
King Stephen and the
Empress Matilda, and was the location of the regional mint. Robert was a supporter of Matilda, and the castle exchanged hands between him and Stephen several times in the next few years, with the town being possibly burnt by Stephen. By the end of the fighting, nearby
Corfe Castle had taken over as the most important military fortification in the region. After 1154 and the end of the civil war, the castle was controlled by the earls of Gloucester. The town's economy stagnated during the late 12th and 13th centuries, although in 1207 the castle, which had been confiscated by
King John, was repaired and used by the monarch as a stopping point on the way to Corfe Castle. After John, Wareham passed to the Earls of Clare, who paid it little attention, and the outer bailey ditch was filled in early in the 13th century. The river silted up and the port declined in importance, with trade focusing on
Poole instead; by the 14th century, the town was in economic decline. ==17th-21st centuries==