Most of the late 20th century wave of reforms in mental capacity or competence law were predicated upon the so-called ‘functional’ model of mental capacity, asking not merely whether a person had a mental disorder or disability but rather whether they were capable of making a specific decision (or decisions) at a specific point of time. This model is now under sustained challenge, most notably from the Committee on the Rights of Persons with Disabilities, and this challenge has focused a spotlight on the difficulty of applying the legally ‘neat’ concepts of the functional model of mental capacity across the full complex spectrum of human life.This paper presents a review, in two parts, of the first ten years of the Court of Protection, a specialist mental capacity court in England and Wales which applies a functional model of mental capacity.The first part outlines the history of the functional model in England and Wales, and the development of this specialist mental capacity court (Court of Protection), created by the Mental Capacity Act 2005. The second part presents an empirical and case-based study of 40 published cases of capacity disputes presented to the Court of Protection, or to the Court of Appeal on appeal from the Court of Protection, during the first ten years of its existence.The authors found that in 70% of cases the subject of proceedings (or P) had either a learning disability or dementia, and the court ruled on P's capacity for a wide range of issues, most commonly residence, care and contact. The judge considered the support principle, or whether practical steps were taken to maximise P's capacity, in 23 of 40 (57.5%) cases. The subject P was determined to have capacity in 13 cases, to lack capacity in 22 cases, and in 5 cases P was found to have and lack capacity for different issues before the court. The functional inability to use or weigh relevant information was most commonly cited by the judge, being cited in all but 2 cases in which P was determined to lack capacity and inabilities were cited. The propensity for the system to learn was shown by an increase in the proportion of cases which considered the ‘causative nexus’ from 2013, when a Court of Appeal case emphasised that impairment must not merely be present alongside functional inability but must be the causal basis of inability.The authors conclude that whilst the Court of Protection is still on a learning curve, its work provides a powerful illustration of what taking capacity seriously looks like, both inside and outside the courtroom. The implications for judges, lawyers and psychiatrists that can be drawn from the study are generalisable to other comparable socio-legal frameworks in which mental capacity or competence plays a role and is likely to do so for the foreseeable future.