The Victorians built places like Claybury with serious intent. The site was chosen on the brow of a hill, surrounded by trees, ponds, pastures, and gardens that had been laid out in 1789 by Humphry Repton, the most famous landscape designer of his era. The idea, taken seriously at the time, was that beautiful surroundings and fresh air were therapeutic in their own right. Claybury was commissioned by the Middlesex Court of Magistrates in 1887, passed to the newly created London County Council in 1889, and opened in 1893 as the Claybury Lunatic Asylum. The architecture - a great central administration block with chapel, water tower, and radiating ward pavilions - was meant to function as a small self-contained community. Many of the people who came here did stay for decades. For some, Claybury was both home and local village by the time they died.

In 1895 the London County Council appointed Helen Boyle as an Assistant Medical Officer at Claybury. She was one of the first women ever employed as a doctor in an English asylum, at a time when most medical schools did not even admit women. Boyle went on to found the Lady Chichester Hospital in Brighton, which pioneered early voluntary treatment for women with mental illness who would otherwise have been certified and committed. In 1939 she became the first female president of the Royal Medico-Psychological Association, now the Royal College of Psychiatrists. The hospital's historian Eric Pryor described her work as 'part of the pale new dawn of community care for the mentally ill'. The hospital's first medical superintendent, Robert Armstrong-Jones, was meanwhile arguing publicly in 1906 that patients should be able to seek help for mental symptoms without losing their liberty - a position that would not become law until the Mental Treatment Act of 1930.

Also in 1895 the LCC appointed Frederick Mott as director of a new research laboratory at Claybury. Over nineteen years Mott carried out a vast programme of work, publishing the Archives of Neurology and Psychiatry between 1903 and 1922. He was knighted in 1919. He is particularly remembered for helping to establish that general paresis of the insane - a devastating progressive dementia then common in asylums - was a late-stage consequence of syphilis. That discovery moved a major category of mental illness from the realm of moral failing or hereditary weakness, where Victorian theory had often placed it, into infectious disease that could be understood and eventually prevented. Claybury was, in a real sense, one of the places where modern biological psychiatry began.

From the mid-1950s, consultants Denis Martin and John Pippard tried something genuinely radical at Claybury: they attempted to turn an entire institution of more than 2,700 people into a therapeutic community. The idea, developed elsewhere on a small scale but never attempted at this size, was that the hospital's social environment - the meetings, the relationships between staff and patients, the structure of daily life - was itself the treatment, not just a setting for treatment. Patients had voices in how their wards ran. Drugs were used sparingly, physical treatments minimised. Martin published Adventure in Psychiatry in 1968; a collection of staff essays edited by Elizabeth Shoenberg appeared in 1972 as A Hospital Looks at Itself. The patient population fell from 2,332 in 1950 to 1,537 by 1970. Critics noted a 'revolving door' problem - over half of admissions were re-admissions - because community care outside the hospital had not yet been built.

By 1968 there were 47 nationalities represented among Claybury's staff. From the late 1940s, with British recruitment increasingly difficult, the hospital had hired widely from Europe and then, after a 1962 proposal from Health Minister Enoch Powell, from the West Indies and Pakistan. The diversity became part of the therapeutic community itself. By 1980 the patient population was 1,057; by 1990, 429. With the Care in the Community programme of the late 1980s and 1990s, hospitals like Claybury faced closure as their long-stay residents were moved into smaller community settings. For many people, who had been on the wards for thirty or forty years and knew nothing else, the move was profoundly difficult. The hospital published its centenary history in 1993 and closed in 1997. The grand main building, tower, and chapel - the chapel now a swimming pool, listed Grade II - became the centrepiece of a gated housing development called Repton Park. The grounds Humphry Repton had laid out in 1789 are still recognisable. The work that was done inside the building is harder to see.