Mills is a fictional British secret agent created by Manning O'Brine in the late 1960s. He played roles of varying importance in three novels, Crambo, Mills, and No Earth for Foxes. He is obsessed with tracking down and killing Nazi war criminals, as apparently O'Brine himself was. In the last novel, No Earth for Foxes, he is retired, happily married, and running a small hotel in Italy. He temporarily leaves his new life to help hunt down and personally kill a notorious and unrepentant wartime criminal.

The backcover blurb for the 1976 American paperback edition of No Earth for Foxes says that Mills's creator, Manning O'Brine, was a former British secret agent who killed his first Nazi in Heidelberg in 1937 and his last one in Madagascar in 1950.