 Most Services were administered by Local Authorities through their Medical Officer of Health and his Ambulance Officer, a few were under the aegis of the Fire Service, whilst others relied upon agency methods for the provision of part or all of their services".The 142 existing ambulance services were transferred by the National Health Service Reorganisation Act 1973 from local authority to central government control in 1974, and consolidated into 53 services under regional or area health authorities.This led to the formation of predominantly county based ambulance services, which gradually merged up and changed responsibilities until 2006, when there were 31 NHS ambulance trusts in England.