4,000-10,000 French soldiers had been killed, according to French sources, and up to 1,600 English. English accounts put the figures at up to 11,000 French deaths and fewer than 100 English. What about the killing of prisoners? There’s no doubt Henry ordered his men to execute their captives (“Every soldier kills his prisoners,” Shakespeare has him say); most historians think he did so in the early afternoon, some hours into the battle, after a French counterattack had made him think the French were regrouping and might liberate their captured comrades. But the order was not condemned by chroniclers on either side at the time.

Is that because the French would have behaved similarly?

Almost certainly. The French saw the English army as rebels in a civil war rather than foreign invaders. At Agincourt, their knights were flying the “Oriflamme” – the red banner on their lances signifying that no mercy would be shown to the enemy. Besides, such rules of chivalry as did exist only applied to high-status captives such as knights (who were traded for ransoms), rather than common soldiers, who had no guarantee of decent treatment. One contemporary eyewitness source has Henry telling his archers that if captured, they could expect the French to cut off their first two fingers. (This could have been the basis for the myth that the V sign had its origins at Agincourt.)

But is it sensible to depict such actions as war crimes?

They certainly seem in breach of some chivalric rules of fighting. In his Tractatus de Bello (1360) Giovanni da Legnano, a Bolognese lawyer, wrote that mercy should be shown “to persons captured in a lawful war”. Christine de Pisan, writing in France around the time of Agincourt, states that a knight should not be “cruell” to his prisoners or “tormente or make them to langwysshe in pryson”, but treat them “goodly and humaynely”. By the 15th century, however, as new technology, like powerful bows, made warfare less personal, old customs of knightly combat were receding. In any case, it’s absurdly anachronistic, says British historian Andrew Roberts, “for French historians to use the language of human rights when describing medieval warfare”. Calling Henry V a war criminal, says another British historian, is like accusing the Romans of animal welfare abuses in the Colosseum.

And the French reaction?

“I never once used the phrase war crime,” protests museum director Christophe Gilliot, who berates the British for yet another piece of mythmaking on St Crispin’s Day. “This wasn’t even a big conference of French academics,” he insists. “The most famous person there was the mayor of Agincourt.”

Hundred Years War or French civil war?

Agincourt was one battle in a 116-year-long conflict that is usually regarded as a series of Anglo-French wars. Equally, though, it can be been seen as a French civil war: in 1328, a succession crisis gave England’s Plantagenet kings, descended from the Normans, a creditable claim to the French throne. The Hundred Years War that followed was a struggle for the throne, fought between two aristocratic houses, the Plantagenet and the Valois, with French soldiers on both sides. Henry V died of dysentery in 1422, but by that time he had secured the Plantagenet claim to the French crown. His son, Henry VI, was crowned King of France in Paris in 1431. But the house of Valois, inspired by Joan of Arc and the Dauphin, the future Charles VII, succeeded in expelling the Plantagenets from most of France in the 1450s. The war was a milestone in the development of both French and English ideas of nationality; it left England an island nation, shorn of almost all its continental possessions. Militarily, it saw the introduction of the first standing armies in Western Europe since Roman times. In France, the conflict, along with the Black Death, reduced the population by two-thirds.