Everyone knows that King John (r. 1199-1216) was bad. In 2009 listeners to Melvyn Bragg’s BBC Radio 4 programme In Our Time were told by the medieval historian Nicholas Vincent that ‘John really was an absolute rotter through and through; the worst king in English history.’ Here is a monarch, it is argued, whose character was so ill-suited to the delivery of effective governance that it was inevitable that his reign should be one of misdeeds and failures. The loss of Normandy; the marriage to Isabella of Angoulême; the murder of Richard I’s designated heir Arthur; the prolonged contest with Pope Innocent III; the acts of cruelty against Jews and other members of the political nation; and John’s lustfulness towards the wives of his barons – all are perceived as wayside markers pointing to the inevitable climax of the reign: baronial revolt and Magna Carta. Since his own day – apart from a period in the 16th century when he was temporarily rehabilitated by the Tudors because of his resistance to Innocent III and some revisionism undertaken in the 20th century – it has been commonplace to portray John as fatally flawed. ‘Foul as it is, Hell itself is defouled by the foulness of John’, concluded the chronicler Matthew Paris (c. 1200-59). John was literally diabolical.

John’s reputation suffered at the hands of chroniclers even before he became king. Among the most important sources for his early years are Richard of Devizes, who ended his Chronicon de rebus gestis Ricardi Primi in 1192, and William of Newburgh, whose Historia rerum Anglicarum ceased at the author’s death in 1198. Roger of Howden, author of Gesta Regis Ricardi, and Ralph of Diceto, author of Ymagines Historiarum, ended their chronicles in 1201 and 1202 respectively. All provide devastating early assessments of John. William of Newburgh, for example, commenting upon John’s alleged treachery towards his brother while Richard was absent on crusade, concluded that John...