[5] Neither the Fox nor the Davies families were armigerous, so in 1905, when Fox-Davies was 34 and already well-advanced in his career as a writer on heraldic and genealogical subjects, he organised posthumous grants of arms to both his grandfathers.

[citation needed] In addition to his writings on heraldry, he published a number of works of fiction, including detective stories such as The Dangerville Inheritance (1907), The Mauleverer Murders (1907) and The Duplicate Death (1910).

In support of this campaign, he produced a directory which attempted to list all living bearers of arms in England and Wales who could prove such authority, under the title Armorial Families.

The most lavish of these was The Art of Heraldry: An Encyclopædia of Armory, which was originally conceived as an English translation of a German publication (Ströhl's Heraldischer Atlas) but which was transformed, in Fox-Davies's hands, into a largely original work specifically directed to the history, theory and practice of English heraldry, with illustrations in black and white and in colour throughout.

Much of the material in this book was re-used in a shorter, cheaper and more popular exposition of contemporary English heraldic practice, A Complete Guide to Heraldry, which proved very successful and influential.

Fox-Davies's emphasis on practical and officially authorised heraldry caused him to showcase mostly recent grants of arms.

This was in contrast to the medieval emphasis of other scholars, of whom his most prominent critics were Oswald Barron, author of the celebrated article on heraldry in the 1911 edition of the Encyclopædia Britannica, and Horace Round.

Round, in an essay called "Heraldry and the Gent" (eventually published in his collection Peerage and Pedigree), ridiculed another thesis with which Fox-Davies was particularly associated, namely, that an English grant of arms was equivalent to a continental patent of nobility, and that, not only were all English armigers to that extent noblemen as well as gentlemen (if male), but that no one without an official right to bear a coat of arms could claim to be a gentleman at all.

Fox-Davies never served as a herald or pursuivant at the College of Arms, but he was one of the 250 Gold Staff Officers who assisted at the coronation of King George V.[3]