Rufus’s reign is marked in the administrative sphere by extremes of avarice. The king was in constant need of revenue in order first to secure his throne in the face of rebellion from the supporters of Duke Robert, and then to prosecute his struggle against Robert for Normandy. This occupied most of the period 1089-96, when a settlement was reached in order to enable Robert to leave his duchy and go on crusade. Rufus exploited the profits of the feudal system to the fullest extent. During episcopal vacancies, the revenues of the lands of the bishopric were due to the crown. Rufus therefore allowed bishoprics to remain vacant for lengthy periods and, unprecedentedly, demanded feudal reliefs when new bishops were eventually appointed. Sheriffdoms were also bought and sold, and those families which already regarded a particular sheriffdom as their hereditary due were willing to pay large sums for the office.