The daring commando raid behind enemy lines. The dummy pass that outwits the defender and enables the match-winning try. The superhero concealing their true identity behind a mask. Examples of admirable deception abound in our culture. Yet deceit and trickery are also the tools of the con-artist, the spin doctor and the terrorist. In April 2017, Afghanistan's Defence minister, Abdullah Habibi, and army chief of staff, Qadam Shad Shahim, both resigned after a Taliban force was able to enter an Afghan army base disguised as injured soldiers, wearing bandages and arm drips, resulting in the death or injury of up to 170 people. Our attitudes to deception are profoundly ambiguous and contextual.

Medieval Europeans could be similarly ambiguous in their opinions on deception. Medieval literature is full of tricksters, both heroic and surprisingly amoral. Clerics, charged with guarding society's spiritual and moral health, diligently preserved exemplars of military deception inherited from the Classical world and recorded similar tales in their contemporary histories. And combatants, even chivalrous knights and nobles, appear to have been perfectly willing to use ambush, disguise and other forms of trickery to gain an advantage in battle.

The idea of a ‘chivalrous trickster’ may sound like a tautology to many modern readers. When we talk about ‘chivalry’, we associate it with honour, good manners and ‘fair play’ and assume that these values have some distant origin in medieval culture. This view is compounded by a simplistic depiction of medieval warfare in certain popular histories: ‘Opposing armies generally continued to form up a thousand meters apart and basically to leap, grunt, and hack at each other […] campaigns were conceived of in terms of individual battles and victory was something to be exploited for plunder rather than pursuit’. Specialist study over the past fifty years has greatly advanced our understanding of medieval warfare beyond this crude stereotype. For the period 1050–1320, commonly referred to as the Central or High Middle Ages, the work of scholars such as John France, John Gillingham and J. F. Verbruggen has revealed a level of strategic and tactical complexity to medieval warfare that is greatly at odds with the image of primitive warriors charging headlong at one another.