Under the provisions of the Asylums Act 1853, the Corporation of London was empowered by statute to provide an Asylum to house the insane of the City of London. Land was acquired at Stone, near Dartford, Kent, in 1859 and in July of the same year James Bunstone Bunning, the City's Clerk of the Works (later City Architect and Surveyor), was instructed to prepare plans and estimates. These were laid before the special Lunatic Asylum Committee at the end of September 1859. Initially provision was made for more than 300 patients but this was reduced to 250 by the Commissioners in Lunacy in 1860. The Asylum was officially opened on 16th April 1866 and was managed by a Committee of Visitors composed of Aldermen and JP's.
By 1872 the asylum was full and extensions were necessary. Development soon began on a new wing, opened in 1875. The passing of the 1890 Lunacy Act meant the Hospital could take advantage of the authority contained therein and admit private patients. From 1st January 1892 it was in a position to do so; and by 1897 such was the demand for accommodation of private patients - who wore their own clothes, had improved dietary provision and had separate wards from the pauper patients - that some admissions were declined. By 1910 305 of the 610 patients in the hospital were private. By 1921 the number of private patients had risen to 357.
By November 1905, the Visiting Committee wanted to adopt the description 'City of London Mental Hospital' instead of asylum. The 1923 Mental Treatment Bill confirmed the term 'Mental Hospital' replaced 'Asylum'; and from 1924 the name of the hospital was changed to the City of London Mental Hospital. After the Local Government Act 1929 conferred upon the London County Council the mental and isolation hospitals formerly run by the Metropolitan Asylums Board (MAB) and local Boards of Guardians, there was discussion over whether the City of London Mental Hospital should be similarly transferred. The Visiting Committee strongly opposed this and it was agreed the hospital could remain under the auspices of the City of London. In July 1948 the Hospital passed out of the Corporation's administrative control into that of the NHS.
During April 1948, the Darenth and Stone Hospital's Management Committee (DSHMC) was set up as part of the transferral programme of hospitals into the NHS. The other hospitals in the group were Darenth Park and Mabledon Park, Maidstone. All apart from Stone House had been previously run by the LCC. Re-organisation of the Heath Service in June 1971 meant that Stone House and Mabledon and Darenth Park amalgamated with the Dartford Hospital Management Committee, forming the Dartford and Darenth Hospital Management Committee.
In April 1973, when Health Boards were re-organised again, this time as Area Health Authorities, the hospital group came under the Dartford and Gravesham Heath District. In 1998 the Trust in charge of Stone House, Thameslink Healthcare NHS, agreed the hospital was no longer suitable for provision of modern healthcare and would be closed in line with Department of Health policies. This decision was carried forward by the next healthcare providers Thames Gateway NHS Trust. The West Kent NHS and Social Care Trust started the work of closing the hospital in 2003, and after 139 years of service, Stone House finally closed in 2005. The main hospital, chapel, service blocks, and staff accommodation presently survive largely unaltered - they are Grade II listed - but are becoming run down and await suitable redevelopment.
See also website managed by Francine Payne: http://www.dartfordhospitalhistories.org.uk/ (correct as of August 2010).