Centuries after his death Díaz, a mercenary war-lord who sold his services as often to Muslim rulers as to Christian ones, was reinvented by the propagandists of the Counter-Reformation as a knight-crusader battling the infidel. His acts of aggression were given a sacred justification: his “pitiless blows” were presented as the means whereby the benighted might be brought to the infinite mercy of the Christian God. But his contemporaries saw Díaz plain. His admirers celebrated him for his splendid successes in robbing his competitors, and for what seemed to them his unequivocally commendable capacity for killing people. Even Ibn Bassam, the contemporary Arabic historian who chronicled some of his worst atrocities, called him “the scourge of his times”, “that tyrant whom God should tear to pieces”, but also “one of the greatest of God’s miracles”.

We no longer, it seems, want such a whacker and thwacker for a hero. The citations for the servicemen and women awarded medals last month laid great stress on the lives they saved, but made only euphemistic mention, or none at all, of those they may have taken. Private Johnson Beharry, now a holder of the Victoria Cross (VC), was on a rescue mission in Iraq when he drove into an ambush and he subsequently returned repeatedly to a burning tank, under heavy fire, to help other British soldiers to safety.

His story, as we have been told it, is one comparable not to the bloodthirsty “Contes de Gestes” in which warriors were celebrated for their kill-count, but to the uplifting narratives — that began to appear in print in the mid-19th century and are still a staple of our popular culture — about brave firefighters, nurses, lifeboatmen and unarmed police who risk their lives for the common good.

At the time of the Falklands war, 23 years ago, when the last Victoria Crosses were awarded, the British public was still ready to honour aggressors. Lt Colonel “H” Jones and Sergeant Ian McKay were each granted a VC for courage displayed in leading an assault. But then, both men had died in the course of the attacks, and a soldier who has given his life automatically takes on the character of a spotless sacrifice. Had Jones and McKay, by some freak of change, survived the risks they so courageously took, it is possible that the public would have revered them less, even then. Now, in a progressively demilitarised culture and in the wake of an unpopular war, the kind of altruistic, non-aggressive valour for which Private Beharry has been decorated is the only kind we can unreservedly applaud.

It is a cultural shift that should probably be welcomed. This nation’s heroes, beginning with the legendary bandit Robin Hood, are a morally suspect lot. Francis Drake, with whose story Michael Howard wishes every British schoolchild to be conversant, was not only a prodigiously gifted seaman but also a slave trader, a terrorist and a pirate. When he returned from his circumnavigation of the world, the hold of his ship packed with stolen silver, Queen Elizabeth knighted and indulged him in exchange for a regal share of the loot, but there were those more scrupulous, her first minister Lord Burghley among them, who refused to shake his hand. Drake didn’t even observe the code of honour said to pertain among thieves. In Panama in 1572, he declined to turn back to rescue a wounded fellow-pirate, Guillaume Le Testu, abandoning him to the Spanish, who cut off his head. Drake may be our national hero, but he certainly wouldn't be eligible for a VC.

His contemporaries admired audacity and readily condoned violence. We set more store by public-spiritedness, and are so ambivalent in our feelings about warfare that we have nearly deluded ourselves it is just a form of social work. We have gained in moral sensitivity, perhaps, but we have lost in clarity. Wandering the web looking for information about Beharry, I came upon this lucid and terrible passage from the 14th-century Froissart’s Chronicles: “There were young knights among them who had never been present at a stricken field. Some could not look upon it, some could not speak. They held themselves apart from the others who were cutting down prisoners at my lord's orders. Then an aged knight of Burgundy, who had been sore wounded in the fight, rode up to the group of young knights and said: ‘Are ye maidens with your downcast eyes? Look well upon it. See all of it. Close your eyes to nothing. For the battle is fought to be won, and this is what happens if you lose.’ ”

We don’t kill our prisoners now, as El Cid and England’s heroic Henry V both did. But we do close our eyes, setting up the image of a blameless hero as a screen to hide the realities of conflict.

Lucy Hughes-Hallett will discuss heroism with General Sir Peter de la Billière and others at the festival on Saturday, April 16, at 2pm

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