The third historian to write about the prisoner of the Iles Sainte-Marguerite was Lagrange-Chancel. He was just twenty-nine years of age when, excited by Freron's hatred of Voltaire, he addressed a letter from his country place, Antoniat, in Perigord, to the 'Annee Litteraire' (vol. iii. p. 188), demolishing the theory advanced in the 'Siecle de Louis XIV', and giving facts which he had collected whilst himself imprisoned in the same place as the unknown prisoner twenty years later.
"My detention in the Iles-Saint-Marguerite," says Lagrange-Chancel," brought many things to my knowledge which a more painstaking historian than M. de Voltaire would have taken the trouble to find out; for at the time when I was taken to the islands the imprisonment of the Man in the Iron Mask was no longer regarded as a state secret. This extraordinary event, which M. de Voltaire places in 1662, a few months after the death of Cardinal Mazarin, did not take place till 1669, eight years after the death of His Eminence. M. de La Motte-Guerin, commandant of the islands in my time, assured me that the prisoner was the Duc de Beaufort, who was reported killed at the siege of Candia, but whose body had never been recovered, as all the narratives of that event agree in stating. He also told me that M. de Saint-Mars, who succeeded Pignerol as governor of the islands, showed great consideration for the prisoner, that he waited on him at table, that the service was of silver, and that the clothes supplied to the prisoner were as costly as he desired; that when he was ill and in need of a physician or surgeon, he was obliged under pain of death to wear his mask in their presence, but that when he was alone he was permitted to pull out the hairs of his beard with steel tweezers, which were kept bright and polished. I saw a pair of these which had been actually used for this purpose in the possession of M. de Formanoir, nephew of Saint-Mars, and lieutenant of a Free Company raised for the purpose of guarding the prisoners. Several persons told me that when Saint-Mars, who had been placed over the Bastille, conducted his charge thither, the latter was heard to say behind his iron mask, 'Has the king designs on my life?' To which Saint-Mars replied, 'No, my prince; your life is safe: you must only let yourself be guided.'
"I also learned from a man called Dubuisson, cashier to the well-known Samuel Bernard, who, having been imprisoned for some years in the Bastile, was removed to the Iles Sainte-Marguerite, where he was confined along with some others in a room exactly over the one occupied by the unknown prisoner. He told me that they were able to communicate with him by means of the flue of the chimney, but on asking him why he persisted in not revealing his name and the cause of his imprisonment, he replied that such an avowal would be fatal not only to him but to those to whom he made it.
"Whether it were so or not, to-day the name and rank of this political victim are secrets the preservation of which is no longer necessary to the State; and I have thought that to tell the public what I know would cut short the long chain of circumstances which everyone was forging according to his fancy, instigated thereto by an author whose gift of relating the most impossible events in such a manner as to make them seem true has won for all his writings such success—even for his Vie de Charles XII"
This theory, according to Jacob, is more probable than any of the others.
"Beginning with the year 1664.," he says, "the Duc de Beaufort had by his insubordination and levity endangered the success of several maritime expeditions. In October 1666 Louis XIV remonstrated with him with much tact, begging him to try to make himself more and more capable in the service of his king by cultivating the talents with which he was endowed, and ridding himself of the faults which spoilt his conduct. 'I do not doubt,' he concludes, 'that you will be all the more grateful to me for this mark of my benevolence towards you, when you reflect how few kings have ever shown their goodwill in a similar manner.'" ( 'Oeuvres de Louis XIV', vol. v. p. 388). Several calamities in the royal navy are known to have been brought about by the Duc de Beaufort. M. Eugene Sue, in his 'Histoire de la Marine', which is full of new and curious information, has drawn a very good picture of the position of the "roi des halles," the "king of the markets," in regard to Colbert and Louis XIV. Colbert wished to direct all the manoeuvres of the fleet from his study, while it was commanded by the naval grandmaster in the capricious manner which might be expected from his factious character and love of bluster (Eugene Sue, vol. i., 'Pieces Justificatives'). In 1699 Louis XIV sent the Duc de Beaufort to the relief of Candia, which the Turks were besieging. Seven hours after his arrival Beaufort was killed in a sortie. The Duc de Navailles, who shared with him the command of the French squadron, simply reported his death as follows: "He met a body of Turks who were pressing our troops hard: placing himself at the head of the latter, he fought valiantly, but at length his soldiers abandoned him, and we have not been able to learn his fate" ('Memoires du Duc de Navailles', book iv. P. 243)
The report of his death spread rapidly through France and Italy; magnificent funeral services were held in Paris, Rome, and Venice, and funeral orations delivered. Nevertheless, many believed that he would one day reappear, as his body had never been recovered.
Guy Patin mentions this belief, which he did not share, in two of his letters:—
"Several wagers have been laid that M. de Beaufort is not dead! 'O utinam'!" (Guy Patin, September 26, 1669).
"It is said that M. de Vivonne has been granted by commission the post of vice-admiral of France for twenty years; but there are many who believe that the Duc de Beaufort is not dead, but imprisoned in some Turkish island. Believe this who may, I don't; he is really dead, and the last thing I should desire would be to be as dead as he",(Ibid., January 14, 1670).