The date that the castle was built is unclear. Between 1154 and 1175 it was in possession of the
Earl of Cornwall and it had become a royal possession by 1185. Both
Henry III and
John spent money on the castle. It appears to have been disused from about 1290 and there are references to its stonework being reused by the Chidlock family to build
Dorchester Greyfriars in 1309. Certainly it was abandoned by 1422.
Dorchester Prison occupies its site – originally to the north of the town, with a
Franciscan Priory further east, but nothing of the castle or the priory remain. However, in 1720, two underground passages were discovered while building a chapel: these once connected the castle to the town proper. In the 1800s, a bastion-like rampart still existed, and a small rampart and ditch were visible on the north and east sides.
Great Western Railway Castle-class locomotive No.
4090 was named after the castle. ==Governors==