Taking William Marshall at his word, a comparison of his Defence of Peace of 1535 with the Latin editio princeps of the Defensor Pacis , printed in Basle in 1522, reveals that there is much need for ‘correction’ or rather, it reveals that Marshall had himself corrected and amended the original to suit his own purposes. What those purposes were, the nature of the amendments and their consequences for our understanding of the royal ecclesiastical supremacy will be the subject of this essay.