Construction of a new "Colony for Mental Defectives" began in 1929 in tandem with the Shenley Mental Hospital on the former Porters Park Estate in Hertfordshire. The Middlesex Colony, as it was once called, was designed to house 2,000 patients with various disabilities. It's name changed to Harperbury Hospital at an unknown date, and although a number of buildings have closed it still functions as a school for the disabled.

For some more history and an interesting article about the hospital during World War II, read the BBC article "My Mother, a Nurse at Middlesex Hospital".

04-2009 Update: The empty buildings are being gutted and demolished.