A body of police officers maintained for a police area by a police authority. There are 43 police areas in England and Wales, many of which are based on county boundaries but some of which, such as Thames Valley Police, cover more than one county. Each police area has a police authority. There are normally 17 members of each police authority–nine drawn from the local council, three from local magistrates and five independent members. Police authorities are responsible for maintaining adequate and efficient forces and (except in London), subject to the Home Secretary's approval, for appointing chief constables. (The London forces have Commissioners, and the appointment of the Commissioner of Police of the Metropolis is technically by the Crown.) Police authorities, do not, however, exercise operational or managerial control, although they are responsible for ensuring that authorities comply with their statutory duties of best value. Appointments to a police force, and the direction of its operations, are matters for the chief constable or Commissioner, and its detailed management is largely determined by regulations made by the Home Secretary.