Opened in 1851 to accommodate the pauper lunatics of Middlesex, Colney Hatch Asylum heralded a new dawn of psychiatric care. It grew to become the largest in England but now numbers are dwindling as it prepares for closure. With the help of staff and patients past and present, Dr Roy Porter presents a historical portrait of the hospital and traces its role in the treatment of mentally ill people. Producer Fran Acheson