thumb|right|Spelthorne Borough Council offices, Knowle Green, were opened in 1972. Further reorganisation of the local authorities took place in the second half of the 20th century. Under the London Government Act 1963, Middlesex County Council was disbanded and the Staines UDC area was moved into Surrey. The Local Government Act 1972, which came into force on 1 April 1974, merged the Staines and Sunbury-on-Thames UDCs to form the Borough of Spelthorne.
thumb|right|Spelthorne Borough Council offices Knowle Green were opened in 1972 Further reorganisation of the local authorities took place in the second half of the 20th century Under the London Government Act 1963 Middlesex County Council was disbanded and the Staines UDC area was moved into Surrey The Local Government Act 1972 which came into force on 1 April 1974 merged the Staines and Sunbury-on-Thames UDCs to form the Borough of Spelthorne