This presentation will examine the origins of the mental capacity jurisdiction in England and Wales, now exercised by the Court of Protection, and the way in which for several centuries lay jurymen assessed capacity. It will consider some current practical issues and judicial pronouncements of good practice relating to the assessment of capacity, and briefly touch upon what is likely to happen in the foreseeable future. The underlying theme is that the medical profession was not involved in the assessment of mental capacity until the beginning of the 19th century, but at the end of that century legislation was passed making medical evidence a prerequisite before the court could consider intervening in a person’s life. The United Nations Convention on the Rights of Persons with Disabilities, which the United Kingdom ratified in 2009, is likely to bring an end to the diagnostic threshold and the functional approach towards the assessment of capacity, as well as the application of the ‘best interests’ test when someone is found to lack capacity.