In England, the Care Quality Commission is responsible for monitoring the way the MHA is used and protecting the interests of patients under the Act. The Commission have observed that between 2005–06 and 2015–16, the reported number of uses of the MHA increased by 40%. They proposed a number of factors that influenced the rates of detention, including the increase in population size and in sections of the population ‘at risk’ of detention, especially older people with dementia. Furthermore, there has been a striking change in policy and practice as a result of the Supreme Court judgment in P and Q and P in Cheshire West and how criteria for detention are now applied to people with dementia. The effect of this has meant that most patients with dementia and who lack the capacity to consent to admission to psychiatric in-patient care are now detained under the MHA. We will therefore give a brief overview of the MHA, especially as it relates to dementia, and other practical applications will be dealt with in more detail in the chapters to follow.