In England and Wales, detentions and compulsory treatment under the Mental Health Act have risen significantly over recent years, however police detentions using Section 136 of this Act have risen even faster. It is not clear why. This chapter uses public data and published academic research to review possible explanations. It argues that whilst reductions in services for the mentally ill may account for the general rise in detentions, the emergence of a ‘risk averse’ culture within the police, in which fear of the consequences of a ‘death in police contact’ prompts officers to detain people threatening self-harm, is a primary cause.