The Duchy is a private estate that funds both the charitable and private activities of the Duke of Cornwall.
The site was originally built in 1937, and had been used a children’s hospital until 1990 and as accommodation for medical staff until last year.
The Duchy’s plans also include a former health centre at 65 Sancroft Street, which will be demolished and replaced by a building of 23 flats.
The majority of these flats will be privately rented, with two allocated as affordable housing at a discounted market rent.