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