Few rulers have set in motion developments of such momentous consequence as the emperor Constantine, with his conversion to Christianity in 312 and subsequent halting of the persecution of Christians, ratified a year later in the Edict of Milan. Over the 17 centuries since then, theologians, historians and even novelists, including Dan Brown in The Da Vinci Code, have claimed that a change for the worse in the quality of Christianity (the kind of change an earlier age would have ascribed to supra-natural agents like the Devil or the Antichrist) can be personified in this rather flashy Roman emperor. Even those of less apocalyptic temperament, faced by almost any legacy of the late antique world of which they disapprove – anti-Semitism, the secular power of the church, the rise of intolerance, the spirit of the Crusades – blame it on Constantine.

David Potter. Constantine the Emperor. Oxford University Press, 2013.

Peter Brown reviews Constantine the Emperor in London Review of Books, volume 37, no. 8 (23 April 2015).