"a considerable influence over much of London and the Home Counties"

The Home Counties are those which surround London: Hertfordshire, Buckinghamshire, Essex, Kent, Surrey, Middlesex and Berkshire (since 1963, the latter two have been excluded).

The reason for the name "home" counties may be their proximity to Parliament in Westminster, or it may be connected to the Home Circuit Counties, the jurisdiction of Circuit Judges in the counties surrounding London.