In addition to the problems of construction, the marshy site fostered disease, to which the prisoners had little immunity owing to their extremely poor diet. In 1818 the authorities engaged Dr Alexander Copland Hutchison of Westminster Dispensary as Medical Supervisor, to oversee the health of the inmates. In 1822–23 an epidemic swept through the prison, which seems to have comprised a mixture of dysentery, scurvy, depression and other disorders. The decision was eventually taken to evacuate the buildings for several months: the female prisoners were released, and the male prisoners temporarily transferred to the prison hulks at Woolwich, where their health improved.