When Sir John Franklin's north-west passage expedition sailed in the early summer of 1845 it took with it the hopes and aspirations of the entire nation. This was not, however, to be an expedition for national gain - for it had long been realised that the passage would have no commercial or military value - but be one of benefit to the whole world. It would complete the geography of northern America, perhaps find new lands and peoples, and bring to an end, once and for all, the centuries-old question about the actual existence of the passage.

By any measure it was to be a noble undertaking, and one not without risk. Both Franklin, his ships' companies, and the nation knew of the dangers involved, but HMS Erebus and HMS Terror sailed from England with the latest technology in ship design and with a large proportion of his victualling supplies in air-tight cans - a method of preservation that had been refined over the preceding half century. The officers and men also sailed with the confidence of volunteer seamen, each armed with the mid-Victorian certainty in a Christian God who would either bring them safely through the perils ahead, or keep a place for them at his side should they lose their lives in the attempt.

When the expedition ships failed to emerge into the Pacific, the Admiralty sent out a large number of search expeditions in an attempt to discover their fate. Some evidence was found, but the actual path of the vessels remained a mystery until a Hudson's Bay Company employee - Dr John Rae - came across a group of Eskimos who had in their possession numerous items that could have come only from the Franklin Expedition. This information led to two inevitable conclusions. Firstly, that the expedition had met with disaster and, secondly, it had ended somewhere in the region of King William Island. But that was not all the information that Rae claimed to have discovered.

John Rae seems to have had an almost pathological hatred of the Royal Navy. His survey of Pelly Bay had been ignored by the Hydrographic Department when they issued charts of the area and his planned expedition up the Mackenzie River was ruined by the Franklin searches (thus delaying his long-sought-for Founder's Gold Medal of the Royal Geographical Society). The Hydrographer (Captain Beaufort), in agreement with Captain Parry and Sir John Richardson - all close friends of Franklin - made public their disagreement with Rae over the positioning of Fort Hope - his expedition base at Repulse Bay. He referred to naval officers as 'bunglers' and 'self-sufficient donkeys' and, on one occasion, physically threatened Beaufort's successor.

When he insisted that, by adopting native clothing and methods of survival, naval expeditions would be better equipped to travel in the north, the Admiralty (quite properly) replied: "The prime consideration of fox-hunting is not the killing of the fox, but the observance of good form during the pursuit and the kill. The objective of polar exploration is to explore properly and not to evade the hazards of the game through the vulgar subterfuge of going native."

On his return with the Franklin news, other naval officers were quick to point out that, despite being within days of the site of the tragedy (and with the - admittedly slight - possibility of there still being survivors), Rae had raced home to claim the reward for finding the fate of the missing expedition.

All this, however, paled into insignificance when Rae revealed his most startling news. He claimed to have learned from the natives that Franklin and his men '... had been driven to the last resource - cannibalism - as a means of prolonging existence.' Predictably, a storm of outrage swept across the land. Charles Dickens wrote that Franklin's men could never have resorted to such a horrible practice through their "... own firmness, in their fortitude, their lofty sense of duty, their courage, and their religion." The 'Sun' newspaper was aghast, "... the gallant Sir John Franklin a cannibal - such men as Crozier, Fitzjames, Stanley, Goodsire, cannibals!". 'Many jostling seamen' threatened to attend Rae's lecture to the Royal Geographical Society, and Lady Jane Franklin dismissed him simply as "hairy and disagreeable". Although not noted at the time, Rae had come across the Franklin relics at the same time as a true tale of contemporary cannibalism on the Donner waggon-train was sweeping across North America. He could not have been unaware of the story and its effect. It would have taken very little imagination to have dressed the fate of the Franklin expedition in the same tawdry rags.

Subsequent 19th century expeditions into the same area met with the same tales of cannibalism - from the same people who had met Rae. Almost all the tales were, at best, second-hand and extremely fanciful (e.g. boots full of cooked human flesh that had not been eaten by humans or animals). Other tales were simple misinterpretation, such as that told by the only actual witnesses. They talked of evidence of cannibalism from hands being 'sawed' off the frozen bodies - a common practice, carried out by surgeons, when the hands are so badly frost-bitten that gangrene had set in and the life of the patient was threatened. Yet their accounts talked of the hands being removed for cannibalism. The cannibalism myth had almost died a natural death when it was resurrected by a Canadian academic, Dr Owen Beattie, in 1981. He found a human bone with one end chewed off and 'cut marks' a little further down. These marks, he claimed, were caused by edged implements and represented, therefore, further evidence of cannibalism, despite the fact that the marks were in just such a position where an animal might have held the bone in its claws to chew its end off.

Even more dramatically, a Canadian expedition under the direction of a school teacher named Barry Ranford found a large number of bones at Erebus Bay, a key site in the Franklin Expedition's attempt to make their way to the south and safety after the ships had been abandoned in 1848. Of the almost 400 bones found, 92 proved to have cut marks with over half having multiple cut marks. Subsequent scientific examination suggested that the marks had been caused, yet again, by edged implements such as knives (remarkably, however, none were found to have been caused by animals). Once again this evidence was brought forward as proof of cannibalism.

This 'proof', however, depended upon two assumptions. Firstly, that the only way for cut marks to find their way onto bones was by cannibalism, and secondly, that the only people in the region to have access to edged implements were Franklin's men themselves. On both counts the assumptions are wrong.

When carving flesh from a bone it is quite difficult to cause cut marks on the bone (unless deliberately intended). It is even more difficult to explain how such marks can be found in groups - especially where the marks run at right-angles to the length of the bone. To have made such marks the knife would have had to have been used to hack repeatedly at the same spot - hardly the action of someone slicing meat off.

When, in 1831, Captain Sir John Ross abandoned his ship 'Victory' on the eastern shore of the Boothia Peninsular he left the natives in possession of a vast amount of that rarest of Arctic commodities - metal. This local tribe - the Netsilik - were already known to have been an aggressive people who had driven other tribes out of the area. Now they had ready access to metal tools and weapons, and a tradition (based on Ross's visit) of blaming white men for failures during the hunting season. The scurvy-ridden men making their way down the western coast of King William Island would have been seen, not merely as a challenge to the survival of the Netsilik, but also as yet another source of unimagined riches. The Netsilik, in common with other tribes and peoples across North America also had a tradition of mutilating the bodies of their victims. Not only would this account for the repeated hacking marks on many of the bones, but would also account for the broken limb bones (claimed by the cannibalism theory supporters to have been broken to extract the marrow). It would also account for the missing face of a skull found by Dr Beattie.

It is also worth noting that, among the bones found on the Ranford expedition, were a number belonging to an individual aged between 12 and 15. As such bones could not have come from any of Franklin's men they could have come only from the natives. The possibility that such a young man could have been a casualty during an attack on Franklin's men should not be overlooked.

Furthermore, many of the cut marks were found on finger bones. As the hands are an unlikely place for a cannibal to look for meat, it may be safely assumed that such marks are evidence of any individual trying to fend off an attack by using his hands. When looked at rationally, such evidence that survives from the Franklin Expedition cannot be used to support a theory proposing cannibalism. On the contrary, all the evidence points to an attack on a group of scurvy-weakened men by natives armed with metal weapons.

Could lead poisoning have contributed to the failure of the Franklin Expedition? Dr Beattie exhumed three bodies known to have come from the expedition. Tests on the bones and hair of the well-preserved remains revealed very high lead levels. Not only had the men been suffering from lead poisoning (or so it seemed to Dr Beattie), but the source of such an ailment was readily at hand. The cans used for the preservation of the expedition's meat and soup were found in great quantities close by the graves and proved to have been crudely soldered together leaving great lumps of lead-rich solder in contact with the contents. With the publication of these findings yet another myth attached itself to the Franklin story.

But the 'lead-poisoning' theory is riddled with flaws. The men were middle-Victorians who had grown up amongst the lead-filled pollution of Victorian towns and cities, and both town and country water supplies arrived in lead pipes. Lead paint was universally used both at sea and ashore. At sea the men would have used lead-glazed pottery, drunk water from lead-lined tanks, and eaten food that had been wrapped in lead foil. Clearly the tolerance to lead of mid-Victorians was conditioned by their environment and was much higher than late 20th century generations.

Even the causes of death of the bodies disinterred by Dr Beattie point to straightforward pneumonia or tuberculosis, or a combination of both. The contemporary treatment for such illnesses consisted of lead-based medicines.

The lead content of the hair used to support the lead-poisoning theory can be markedly affected by its environment. Not only could the wood shavings on which the deceased's head lay have introduced lead into the hair, but one of the men - John Torrington - was a stoker who worked in the lead-enriched environment of HMS Terror's boiler room. Such environmental effects are uneven and, consequently, the level of lead in a single hair can vary along its length.

But what about the cans? The expedition had three forms of meat available when it sailed. Live animals, salt meat, and canned meat (they would also be able to restock from the numerous birds, seals and bears they would be able to shoot during their journey). The difficulty with salt meat in the past had been the amount of fresh water that it took to soak the meat in order to make it edible, but such constraints would not apply amongst the fresh-water ice of the Arctic. Consequently, the order of using the meat would have been live animals first, then salt meat, then canned meat. Remarkably, however, over six hundred empty cans were found piled up at Beechey Island - very early on in the expedition. Even more remarkable is the fact that, of the thousands of cans that were carried onboard the ships, less than seven hundred in total have been accounted for - and this in an area where the natives would have been eager to obtain such valuable objects as empty metal cans.

Shortly after the ships sailed from England the people of Portsmouth complained about the great stench that was coming from the naval dockyard. The source of the problem turned out to be a large number of cans of meat that came from the same manufacturer as that supplied to Franklin. When examined, the contents turned out to be putrid to such an extent that nearby white paint had turned brown and workmen fainted upon entering the store. Eventually, out of six thousand cans examined, only one in fifteen proved to be fit for human consumption. Other ships supplied with the same manufacturer's cans threw them overboard and nine thousand cans were returned to the dockyard as uneatable. It is not unreasonable, therefore, to assume that the majority of the cans carried by the Franklin Expedition were in a similar state. This would account for the small number of cans remaining along the expedition's route - the others having been thrown overboard.

If then, that had been the case, would enough of the canned meat have been consumed to have led to lead poisoning? And even if there had, could the lead actually contaminate the meat? Not according to food scientists who claim that the lead particles would have migrated to the tin and iron of the can rather than the contents. Tests carried out on 19th century canned food (including cans from the Franklin Expedition) support these findings.

Dr Beattie's response to such arguments was to counter with the fact that the lead found in the bodies and the lead used in the cans had the same isotope ration values. Therefore, he argued, the cans must be the source of the lead found in the bodies. This would be true if it could be proved that the lead used in the cans came uniquely from one source, and that the source was used for no other lead used in the men's environment. Neither proposition can be proven. Furthermore, whereas different isotope ration values cannot come from the same source, similar values do not have to come from the same source, nor do they provide an unchallengeable link between the two values.

Consequently, if the canned food proved so bad that much - even most - of it was rejected, there would not have been enough lead ingested to have poisoned anyone. In addition, the chances of the food becoming tainted by the lead from the soldered seams of the cans is remote in the extreme due to any electrolytic action transferring lead particles to the can itself rather than the contents. Finally, any similarities between the lead isotope ratio values of the samples taken from the bodies and the lead found on the cans has every chance of being merely accidental.

In conclusion, the Franklin Expedition needs no myths to underline its tragedy. One hundred and twenty-nine British seamen went out on an adventure which would bring little advantage to their country yet could benefit the world. All volunteered in the knowledge that they might not return. At most they would get double pay and a story to tell. The modern urge to denigrate brave men is usually a shoddy attempt to gain bogus status at the expense of genuine gallantry. Such denigrators should not go unchallenged.