The estate was formed in the early 18th century.[2] The house was built as a private residence in 1745 and became St Monica's Priory, a Roman Catholic nunnery, in 1886.[3] In 1896 the house was converted into a hospital so allowing the transfer of smallpox treatment services from Highgate Hospital; the new facility became known as Clare Hall Hospital.[3] Following substantial progress towards eradication of smallpox, the hospital converted to the treatment of tuberculosis patients in 1912 and became Clare Hall Sanatorium in 1929.[3]