T. Kerslake, Vestiges of the supremacy of Mercia in the south of England during the eighth century
“ Some of our most learned historians describe the “Middle Saxons” as a very small people, forming a part of the East Saxons; but they are obliged to confess that they find very little to say about them. It is believed that there never was a separate people called Middle Saxons. They have been created out of a snatched analogy, of the mere name “Middlesex,” with “Essex,” “Sussex,” and “Wessex.” There can be little doubt that Middlesex represents the original civitas, or territory, of the local government, of its urbs or burgh of London, the capital of the kingdom of Essex. ”
