Even if a character who vaguely resembled the fabled leader did exist, he would probably have been a Welshman with strong connections to Brittany and whose sworn enemies were the Anglo-Saxons, they said.
The organisers of a conference and exhibition to be held at Rennes university in northern France next month said they will provide ample evidence that the Arthurian legend has continually been updated, often as a sop to English nationalists attempting to revive the Age of Chivalry.
The event, “King Arthur: A Legend in the Making”, will highlight the argument that historians were joined by artists and writers in creating the “fiction” of the legend.
Typical was the Victorian Poet Laureate Alfred Lord Tennyson, who at the height of the British Empire portrayed Arthur as a thoroughly decent Englishman whose manly virtues and trusty sword, Excalibur, were directed towards establishing heaven on earth.
Sarah Toulouse, curator of the Rennes exhibition, said: “King Arthur is a mythical character who was invented at a certain point in history for essentially political reasons.
“If he had really existed there would be more concrete historical traces of him.”
Highlighting Arthur’s fictional nature, Mrs Toulouse said: “These stories deal with universal themes. The earliest fragments of the tales can be traced back to Wales in the seventh century.
“But by the 13th century stories based on the Arthurian legends were being told right across Europe.”
The tale of a knight repelling the hated Anglo-Saxons from Britain’s West Country in around AD500 has always been popular in northern France, with Arthur and his Knights of the Round Table particularly popular with the Bretons.
Rural Brittany, with its rocky, mystical coastline, is a setting for many of the hero’s adventures.
Sir Lancelot, the best known of Arthur’s Knights of the Round Table, was said to have been raised in the mysterious Broceliande forest in the heart of Brittany by Viviane, the Lady of the Lake who kidnapped him as a young child.
Arthur’s diabolical half sister, the sorceress Morgan Le Fay, also had a secret hideaway on the Brittany coast.
Some texts even suggest that the mystical Island of Avalon, said to be Arthur’s final resting place, is in fact the Isle of Aval in northern Brittany.
Despite such antecedents, the French do at least resist trying to claim Arthur as their own.
“It would be out of the question for us to say that,” said Mrs Toulouse.
Referring to the most popular myth, Mrs Toulouse said: “Arthur was an English King who united all of the Britons – in the British Isles and in Brittany – against the Saxons.”
Arthur’s Camelot is said by many to be Cadbury castle, an Iron Age hill fort in Somerset. Stonehenge is said by some to have been built by Merlin, Arthur’s court magician.
A striking feature of the French exhibition is just how quickly the tales of Arthur and his knights spread across Europe to places as far apart as Iceland and Italy, or Spain and Scandinavia.
The oldest known images of the king can be found not in Britain but at the Cathedral of Modena in Italy in a bas-relief dating from around 1120.
By Peter Allen in Paris, The Telegraph