Since you ask, London (Cranfield) is 5 miles further out from Marble Arch than London (Southend) and 8 miles further out than London (Stansted), but 8 miles closer to the capital than London (Oxford) Airport which is the current winner at 58 miles......
Of course there's really only one London Airport, London (City).
Didn't FR rename BOH "London West" years ago? The winner by a mile. It's 100 mi. or so from London.
Isn't there London-Lydd as well?