Nigel was active in draining the Fens, the swampy land around Ely, to increase the agricultural lands around his bishopric. He also fortified the Isle of Ely with stone defences, probably starting around 1140. The remains of one castle on Cherry Hill in Ely probably date to Nigel's fortifications. Early in his time as bishop he was active in recovering lands of the church that had been granted to knights by his predecessors, and soon after his consecration he ordered an inquest made into the lands actually owned by the diocese and cathedral chapter. The bishop spent most of his life in debt, but in the year he died he managed to clear it with his son's help. The monks of his cathedral chapter did not like the fact that they were required to pay for the bishop's appeals to Rome to recover his see, or pay for regaining the king's favour. Their dislike of their bishop is evident in the "Liber Eliensis". The art historian C. R. Dodwell wrote of Nigel's efforts: When ... Nigel ... needed to raise money in order to repair his own political fortunes, he stripped down, sold, or used as security, a quite astounding number of Ely's monastic treasures. These numbered Crucifixes of gold and silver from the Anglo-Saxon past, and they included an alb with gold-embroidered apparels, given by St Æthelwold, and a chasuble, given by King Edgar, which was almost all of gold. A gold and bejewelled textile covering ... was sold to the Bishop of Lincoln, Alexander, who took it with him to Rome as a gift of particular splendour. It is a biting commentary on attitudes of the Anglo-Norman episcopy to Anglo-Saxon art, that it was left to the pope to point out that such an artistic heirloom should never have left Ely in the first place and to order its return.