Historians authenticate the first reference to the gun with an epic re-creation. Steve Farrar reports

A beautiful July afternoon on the edge of the Yorkshire town of Huddersfield. An anxious knot of historians shelters behind a wall. Their conversation has just died.

A wisp of smoke and the urgent hiss of a burning fuse escape from the bulbous, bronze barrel lying on a trestle table, with a large steel-tipped arrow jutting from its mouth. The reconstruction of the earliest known cannon is about to fire once more.

This was the historians' last chance. All the months of study, argument, design and craftsmanship and they had just one more arrow left to test their remarkable creation.

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Twice that day, the boom of the cannon's powder charge had echoed around the police firing range that the team from the Royal Armouries had taken over. And twice the test firings were failures, spraying fragments of arrow across the hillside. Perhaps they had made a mistake. Maybe the medieval illumination they had based their efforts upon was little more than a flight of artistic fantasy.

The slow match burned down to the tiny black powder charge inside the gun. A clap of thunder. The arrow shot several hundred metres into the gorse and heather on the other side of the range.

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Bob Smith, an expert in early artillery at the Royal Armouries, Leeds, recalls: "It flew beautifully - we just stood looking at each other with broad grins on our faces."

No one recorded the reaction of those who witnessed the firing of the original on which the historians' cannon was based. But some-one did sketch it, and the resulting illumination wound up being included in a book given to Edward III in 1326. Curiously, the text -Jon how to rule, by Walter de Milemete - contains not a single mention of guns.

Some believe it is little more than the product of the anonymous artist's imagination rather than an accurate image of a real object. If the picture, now kept in Christchurch College library, Oxford, is authentic, then this is the first reference to a technology that reshaped western civilisation - the gun.

It is not known how cannons were invented. It is possible that the know-how was imported from China via North Africa, but it is equally possible the breakthrough was a European affair. Although the Chinese used gunpowder much earlier than the Europeans, at the very least for fireworks, the English philosopher Roger Bacon had penned a recipe of saltpetre, sulphur and charcoal in the mid-13th century. By the 14th century, cannons were being used across Europe. There are ordnance inventories that record their presence and hints of possible use in battle from the 1320s onwards. It was a time of experiment, says Kelly DeVries, a historian at Loyola College, Baltimore, who helped with the reconstruction project. "England was certainly at the cutting edge - it seems to have caught on very rapidly all over Europe."

There were two distinct varieties: the familiar wrought-iron cylinder that probably used balls of iron or stone, and the smaller cast-bronze guns that generally fired bolts or shot. The Milemete illustration appears to depict the latter. But was it real?

Smith, DeVries and several colleagues from the Royal Armouries set out to see if they could get an identical weapon to work. The previous year they had successfully reconstructed a cannon based on one recovered from the wreck of Henry VIII's flagship, the Mary Rose. This time, however, the task demanded a little more imagination.

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The Milemete illustration is fairly basic, and there is a lot it does not explain. Trying to solve these mysteries provoked argument. One suggestion, for example, was that the bore would have been large to allow the bronze flights on the arrows inside, surrounded by some kind of packing material.

Alternatively, the bore may have been narrow enough to hold the shaft of the arrow, requiring the top of the bolt to jut out and the flights to be fixed half way down. "The debate on what it was like inside went round in circles," says Smith. "So I made a dictatorial decision and went for the simple option."

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The chamber was to be kept small. The cannon was to have a narrow bore. The arrows would have their flights fixed halfway up their shafts.

Smith took the plans to a foundry near Basingstoke more used to dealing with sculptures. They built a wooden model and then cast the metre-long weapon in bronze.

Medieval inventories record buying oak shafts and having bronze cauldrons cut up for flights. So the Milemete cannon would fire oak bolts with steel tips and bronze flights, weighing just under 2kg.

The historians arrived at Huddersfield with the gun, paper cartridges of black powder and three arrows. After the disasters of the first two trials, that final success came when just two ounces of powder were popped into the barrel, the arrow slid down on top of it and a slow match was lit in the touch hole.

"I was sure the illumination was an accurate portrayal, but we were taking chances with the design. The proof came when it worked," says DeVries.

The gun's effectiveness has yet to be tested - more trials are planned. Smith believes it would have packed a hefty punch: "If that bolt hit a horse or the body of a man, it would have done significant damage," he says. DeVries thinks it is more likely the cannon would have been used to spread panic: "Effectiveness in 1326 may have been scaring the heck out of your opponent."

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But the cannon would ultimately go on to change the face of warfare. Edward III, the teenage recipient of the book by de Milemete, was to be among the tactical pioneers of the new technology. Twenty years after he first saw the Milemete picture, he deployed cannon against the French during his great victory at Crecy. It is recorded that the guns were discharged "to cause panic".