We cannot know for sure how Edward the Black Prince earned his sobriquet. For some it was the volatile mixture of his aggressive temperament and brutal conduct in war; for others it derives from his armour, as displayed on his tomb at Canterbury Cathedral. The cover of Michael Jones’s splendid new biography of this compelling warrior depicts the latter, with Edward arrayed in his suit of plate, his long moustache drooping over the mail of his aventail and the palms of his gauntlets pressed together in prayer, as if seeking God’s forgiveness for all the death and misery he has...