Bio:H. Fox

This site claims Henry Fox produced over 200 covers for Badger Books, but also worked for Arrow, Ward Lock, and Pan. A Fellow of the Royal Society of Art, he lived in North London for most of his working life. The research seems to narrow his death date down to 1979 or 1980, but if he had a middle name 'Stanley' then his birth-date is 1899 rather than 1911.

His signature is distinctive, a capital H under "Fox", with a little flourish underlining the X, like so:

Henry Fox at the TARDIS Index File

H. Fox in the ISFDB

Not to be confused with, who seems to have worked much later.