For centuries, it has been believed that King Edward II met his end in Berkeley Castle in 13. Having been captured by an army led by his queen, Isabella, and her lover, Sir Roger Mortimer, he was forced to abdicate in favour of his underage son, Edward III. He was then imprisoned and, according to those chroniclers most biased against his usurpers, was then subjected to a series of torments, including being starved and thrown into a pit full of rotting corpses.

But it was the final torture that made Edward II’s death arguably the most famous in English royal history: a group of men pinned the deposed king beneath a mattress or table, pushed a horn into his anus, and then inserted a red-hot poker that burned out his internal organs. This grisly execution was supposedly devised to leave no visible mark on the body. Although many historians have long suspected that the red-hot poker story was just medieval propaganda, most agreed that Edward II was indeed murdered in 13.

As a result, the death has a rare status in British history: part of the nation’s consciousness of its bloody heritage and a landmark date in works ranging from the Handbook of British Chronology to the tourist guidebooks to both Berkeley Castle and Gloucester Cathedral, where Edward II is buried. This creates huge problems for the historian who discovers that the murder simply did not happen: Edward II did not die in Berkeley Castle.

That no newly discovered documents or recent forensic tests underpin this claim only increases the difficulties he faces. To challenge popular belief on such grounds is by no means unprecedented, but to challenge the consensus of academic opinion in this way is hardly imaginable.

In fact, the idea that Edward II was not murdered was first mooted in 1877 when a French archivist published the text of a copy of an undated letter purporting to be from a papal notary, Manuele de Fieschi, to Edward III.

This reported how the young king’s father had “escaped” from Berkeley Castle and, via Ireland, France and Germany, arrived in Lombardy. The great historians William Stubbs and Thomas Frederick Tout, writing in 1883 and 1919 respectively, could neither believe nor explain the text.

Years later, though, Pierre Chaplais pointed out that royal accounts dated 1338-39 refer to a “William the Welshman”, who claimed with impunity to be Edward II in the presence of Edward III at Cologne and Antwerp. Other documents were published suggesting Edward II’s survival, including the judgment on his half-brother, the Earl of Kent, who was executed in March 1330 for trying to effect Edward’s release from Corfe Castle, even though the deposed king had supposedly been dead for three years.

Against such evidence stood the chronicle reports stating that Edward II had died in Berkeley Castle. More important, a number of Edward III’s own statements attest to the murder, including records of the prosecution of the supposed murderers in the Parliamentary Rolls. The case seemed rock-solid. But recently, the evidence has been reconsidered from the point of view of the supposed murderers, and an entirely different picture of Edward II’s “death” has emerged.

The key to understanding what happened is knowing how news of the king’s death spread. A message that Edward II had died on September 21 13 was sent from Berkeley Castle to Edward III in Lincoln. A public announcement was made after Parliament broke up on September 29, and the news was accepted in good faith. Three weeks later, Lord Berkeley led the funeral cort ge into Gloucester, and the interment took place in late December. But the corpse could have been anybody’s; before leaving the castle, it had been completely covered in waxed cloth and encased within two coffins. As the only chronicler to mention the event put it: the king’s body was exhibited “superficially”.

The rule of Lord Mortimer was brought to an end in October 1330. He was hanged after being judged guilty of a long list of crimes, including Edward II’s murder. He was not permitted to say anything to Parliament in his defence. But Lord Berkeley was allowed to speak. In reply to the question of how he intended to acquit himself of complicity in Edward’s murder, Berkeley stated that he “had not heard that the man was dead until coming into this present parliament”. Many scholars have wondered what he meant by this. Perhaps they should have wondered a little harder, for the entire traditional narrative of the murder followed Berkeley’s initial message that the king had died. Yet here he was admitting that he had lied.

Furthermore, the Parliamentary Rolls confirm that Berkeley shared responsibility with Sir John Maltravers for making sure that no harm came to Edward II while in their custody. But Maltravers, who escaped capture in 1330, was never charged with failing in this duty. Edward III cannot have been trying to protect Maltravers as he was sentenced in his absence to a traitor’s death for the lesser crime of being an accessory to the judicial execution of the Earl of Kent. As one of the two men equally liable, it follows that the charges brought against Berkeley were groundless. Edward III was forced to bring fictitious charges against his father’s jailer to support his sentence against Mortimer. Subsequently, all charges against Berkeley were dropped.

Faced with a correlation of the perspectives of accuser and accused, one can no longer support the traditional narrative of Edward’s death. Those who wish to do so need to undermine the logic of the arguments concerning Berkeley’s testimony and the failure to charge Maltravers if they wish to continue to participate in the debate. Perhaps most interesting of all, there is no longer any justification for dismissing the Fieschi letter as a forgery, or the accounts of William the Welshman as the antics of an imposter. Rather, we should question the reliability of the chronicles with regard to the death, on whose misinformation so many have placed much trust for so long.

We cannot be certain what happened to Edward II after 1330. If the Fieschi letter is correct - and it seems probable that it broadly outlines the facts of Edward II’s later life as he himself understood them - he was released after the execution of Mortimer. He then travelled to Avignon to see the pope, who persuaded him to give up his attempts to regain the throne. If the revised dating of the Fieschi letter to early 1336 is correct, it would appear that he had settled at a hermitage in Lombardy by the end of 1331. It seems likely that the William the Welshman brought to Edward III at Cologne in 1338 was indeed Edward II; he was with the court at Antwerp just after the birth of Edward III’s second son, Lionel. After this, he disappears from the records. The man who presented William the Welshman to Edward III was paid for some secret business three years later that involved several months abroad, possibly to bring Edward II’s remains back from Italy. It is almost certain that Edward II’s remains were placed in Gloucester Cathedral before his son made a pilgrimage there in 1343.

The importance of this debate is, of course, what it means for those studying Edward III and Mortimer, whose tenure of power may well have relied on his secret custody of Edward II. We will probably not be able to discuss such matters until the controversy of Edward II’s survival has been fully ignited, raged and died down. In the meantime, the challenge to the academic establishment is obvious, as is its responsibility to the public in a matter of national heritage.

Ian Mortimer, former library archivist at Exeter University, is now studying for his PhD. His book The Greatest Traitor: The Life of Sir Roger Mortimer, 1st Earl of March, Ruler of England 13-1330 was published last month by Jonathan Cape (£17.99).