Mortain controlled his West Country holdings from his mighty castle at Launceston. He also built Trematon Castle, but most of his time was spent in Normandy or fighting the Danes in Lincolnshire.
In his absence Cornwall came under the control of men like Reginald de Valletort, who held Trematon and Richard, Fitz Turold, Mortain's steward, who held Cardinham.