April 2025 commemorates the 60th anniversary of the abolition of the Ancient County of Middlesex. Much of what we now think of as London north of the Thames, from Hackney in the East LPA: 25062 to Uxbridge in the West LPA: 33284 and Enfield in the North LPA: 33491, was Middlesex. The earliest reference to Middlesex is in a charter of 704 named in Latin as Middelseaxan. By the Domesday survey of 1086 it was divided into six hundreds (Edmonton, Elthorne, Gore, Hounslow, Ossultstone and Spelthorne).

In 1855 as parts of Middlesex became more urban the Metropolitan Board of Works was set up under the Metropolis Local Management Act of 1855. The County was split in January 1889 when the County of London was created from the Local Government Act 1888 mostly separating the more urban areas into London and the more rural areas into the County of Middlesex. In April 1965 both administrative counties were abolished and merged to become Greater London (administered by the Greater London Council until its abolition in April 1986).

Some areas remained semi-rural even after abolition such as Sudbury LPA: 244742 in 1967 and indeed, Harefield (in the modern London Borough of Hillingdon), today.