 In 1263, with others of Simon de Montfort's party Giffard besieged the sheriff of Gloucester in Gloucester Castle.Also in that year, with others, he abducted Peter of Aigueblanche, the Bishop of Hereford, confining him to Eardisley Castle.In 1264 Giffard controlled Kenilworth Castle, and successfully attacked Warwick Castle, occupied by William Maudit, 8th Earl of Warwick.