Originally a castle of earth and wood, the fortress of Le Plessis was owned by Baron Grimoult, one of the most important lords who, along with other Norman barons, assassinated the young Duke of Normandy, Guillaume II, in 1046. known as "bastard" and future conqueror. In 1047 he was one of the leaders of the rebel army that crushed Duke William at the Battle of Val-ès-Dunes. Grimoult, defeated, managed to escape but was pursued by the duke's men, finally captured and imprisoned at Rouen, where he died in captivity, probably oneThe fortress of Le Plessis, originally a castle of earth and wood, was owned by Baron Grimoult, one of the main conspirators who, in 1046, together with other Norman barons, attempted to assassinate young He unnaturally
The wooden structures were probably replaced by a cylindrical stone main tower in the 12th century.