Conisbrough Castle was probably similar to two other castles owned by the Warren earls. Hamelin Plantagenet was also responsible for the development of Mortemer Castle in France, where a similar keep was built on top of a motte, and Conisbrough might also have had resemblances to Sandal Castle in the north of England, also owned by the earls. The design of the keep was poor from a military perspective. The central circular tower provided defensive advantages but the buttresses introduced 12 vulnerable corners into the stonework, and the keep itself had no arrow slots to permit the defenders to fire on any attackers. Rather than being designed primarily for military defence, it was constructed to symbolise and reinforce Hamelin's lordship and new social status.