Chief police officer is a phrase used in the United Kingdom to describe the position held by the most senior police officer in a police force. It refers to either one of the 53 Chief Constables, the Commissioner of the City of London Police or the Commissioner of the Metropolitan Police. Such police officers are members of the Association of Chief Police Officers. The phrase is used in legislation when giving powers such as those to permit public processions, or grant firearms licenses. Some such activities can usually be delegated to any constable.