Genealogy occupied the foremost place in Wagner's affections, but his earliest publications made highly important contributions to the study of heraldry. Issues of State Ceremonial took third priority. His "Historic Heraldry of England" (1939) derived initially from an exhibition of panels in America, but drew a stern and scholarly line between those great men who were truly armigerous and those who were not. On the other hand, his "Heralds and Heraldry in the Middle Ages" (also 1939) shed new light on the development of the functions of the earliest officers of arms. Many years later he traced the whole story of the College of Arms in a massive volume entitled "Heralds of England" (1967). Roy Strong called the book "magisterial".