A survey in 1650 showed that the town houses and their gardens had encroached on the external defences and that the only inhabitable part of the castle was the north gatehouse; the assizes were moved to a new hall built within the town itself. In the same year, Parliament sold off the properties of the duchy of Cornwall, and Colonel Robert Bennett, a Baptist teacher and supporter of Oliver Cromwell, purchased the castle, its deer park and its gaol. The north gatehouse began to be partially used as a prison, and in 1656 was used to hold various members of the Society of Friends, including George Fox, their founder, who described it as a "nasty stinking place".