The decision of the Law Lords in May 1989 that allowed the sterilisation of a woman with serious mental handicap (F. v. W. Berkshire H.A., 1989) is arguably the single most important legal development in relation to psychiatry in the last 30 years. It has far-reaching implications beyond the field of mental handicap and will affect the practice of all psychiatrists. The Law Lords used the appeal to consider “the startling fact that there is no English Authority on the question whether as a matter of common law (and if so in what circumstances) medical treatment can lawfully be given to a person who is disabled by mental incapacity from consenting to it” (Lord Goff). Quite clearly this encompasses a large part of psychiatric practice and promised to clarify much of the controversy surrounding consent and the incompetent patient. The decision that they reached has now been incorporated into the Code of Practice of the Mental Health Act 1983 which was approved by Parliament in December 1989. The effects of this are of huge importance, and it has extensive consequences for all psychiatrists and their patients by simplifying the legal aspects of treatment. The most surprising aspect of this whole issue, therefore, is the silence that has surrounded both the original decision by the Law Lords and the subsequent publication of the Code of Practice. The only reference to these in The British Journal of Psychiatry, or its sister journal, Psychiatric Bulletin, has been a brief letter outlining some implications of the Lords' decision (Lovett, 1989). This is doubly surprising as the Royal College of Psychiatrists has shown considerable interest in this debate, not least by publishing a book about it! (Hirsch & Harris, 1988). The purpose of this paper is to provide a background to the Code of Practice and to clarify certain issues surrounding the Common Law.