Middlesex is a former county of south-east England. The name dates from the Anglo-Saxon conquest of southern and eastern Britain and derives from the term 'Middle Saxons' (contrasted with the 'East Saxons' of Essex and the 'West Saxons' of Wessex). The area of Middlesex corresponds to central, west and north London. The City of London lay within Middlesex until granted self-governing status in [date], and as the city spread outwards from the Middle Ages onwards much of what was known as London lay in Middlesex. In 1888 a partial attempt was made to regularise the situation with the creation of the County of London, which incorporated much (but by no means all) of the conurbation, including territory from Middlesex, Surrey, and Kent. London's continued growth in the late 19th and 20th centuries required further administrative change, and in 1965 the county of Greater London was formed. This incorporated parts of Essex and Hertfordshire, further districts of Kent and Surrey, and almost all of the remaining county of Middlesex. Only Spelthorne and Potters Bar did not become part of the new county: the former was transferred to Surrey and the latter to Hertfordshire.
The name Middlesex is still used by sports and cultural organisations, and by the Post Office (although the PO definition of Middlesex varies greatly from the traditional boundaries). Middlesex County Cricket Club, which has its headquarters at the historic Lords ground, is probably the most widely-occurring usage.
The traditional county was bounded by the River Thames to its south, and by tributaries of the Thames - the Rivers Colne and Lea - to its west and east respectively. The northern boundary was a somewhat meandering 'dry land' line on the edge of the Hertfordshire hills. The southern part of the county is low-lying flat land; the north is more undulating. Almost all of it is covered by Victorian or twentieth century suburbia, and the subject of appreciative poetry by Sir John Betjeman.