of Portchester was granted to William Maudit, an associate of William the Conqueror and a powerful magnate and it was probably he who built Portchester Castle.

The form of this early castle is uncertain, although Maudit was probably responsible for creating the inner ward in the north-west corner of the fort. At this point it would probably have been defended by a wooden palisade and a moat, with the original Roman stone walls of the fort acting as the defence of the outer bailey.