Middlesex is the county of London, like other English counties which are usually named after one big town. It’s sometimes said to be the former kingdom of the Middle Saxons, but William Lethaby’s 1902 history of pre-Norman Conquest London questions whether there actually were any ‘Middle Saxons’ (by analogy with the historical West Saxons of Wessex, the East Saxons of Essex or the South Saxons of Sussex).
Instead Middlesex is one of those rump territories that surround a trading centre or a capital city, like Washington’s District of Columbia, Hong Kong’s New Territories or Canberra’s Australian Capital Territory.
It has always had a unique relationship with London, which, as a world city, has become almost an extraterritorial abstraction, like the numbers in bank ledgers or computer drives that constitute its wealth. Middlesex is home to London and home to many of its people. London and Middlesex an be considered as different aspects of the same geographical entity. ‘London’ is what people endure for the sake of making money; ‘Middlesex’ is where many aspire to spend it, surrounded by trees and bird song.
Middlesex is on what is mostly the north bank of the Thames. (Confusingly though at Richmond the Surrey bank is at times the north bank, and with a river whose tidal flow changes direction twice a day it makes no sense to talk about a ‘left bank’ and ‘right bank’ like in Paris.) Its name is guaranteed to survive to describe the ‘Middlesex bank’ that gives rowers and other river users their bearings. It’s a county of the river basin; its soil is London clay; it is crossed by scores of streams and tributaries of rivers and its boundaries are the Lea to the east, which formed the 878 AD boundary with the Danelaw, and the Colne to the west.
To the northwest Middlesex ends in the foothills of the Chilterns and the lower hills of Hertfordshire. It is very small compared to the other English historic counties: originally 283 square miles, and finally 232 after it had lost territory in 1881 to the new County of London. By comparison Kent has 1,442 square miles.