This chapter traces the history of lunacy investigation law from 1320 to 1890 in England. This body of law included trials in lunacy, chancery court proceedings, proceedings in guardianship and trials of traverse. Verdicts of non compos mentis in these trials meant that individuals were mentally incapable of managing their person or property. Included in this legal approach to madness was the appointment of a guardian who would oversee the care and management, as well as the material wellbeing, of those deemed to be non compos mentis. The law also provided for the restoration of control over property and person in cases where individuals could successfully convince the courts that they had regained their ability to control property rationally – trials of traverse. This chapter argues that the development of lunacy investigation law for the preservation of property in the face of irrational behaviour was central to the definition of and response to madness for centuries in England. It was a socio-legal context for understanding and responding to madness that would eventually be situated in parallel with laws that signalled a growing emphasis on institutional confinement and inspection in England and, later, in parts of North America.