For thirty-four years, a prisoner was moved from fortress to fortress across France under conditions of unusual secrecy, always in the custody of the same jailer, always hidden from the world. When he died in the Bastille on 19 November 1703, his burial certificate bore a name that may not have been his own. His true identity has never been established. This article presents what the surviving records actually say, and separates that record from the legend that grew around it.
The record: arrest and imprisonment
The earliest surviving records of the prisoner date from July 1669. On 19 July of that year, a warrant was issued for the arrest of a man named “Eustache Dauger.” On 28 July he was arrested near Calais by Captain Alexandre de Vauroy, garrison commander of Dunkirk, and on 24 August he was imprisoned in the fortress of Pignerol, in what is now north-western Italy but was then French territory.
The order came from the Marquis de Louvois, Louis XIV’s secretary of state for war, who wrote to Bénigne Dauvergne de Saint-Mars, governor of Pignerol, to expect the prisoner. Louvois’s letters describe Dauger in strikingly vague terms: the prisoner was “only a valet,” held for what he had done — or what he knew. No charge was ever stated in any surviving document, and no trial is recorded.
For the next thirty-four years, the prisoner followed Saint-Mars from posting to posting. He was held at Pignerol from 1669 to 1681, at the fort of Exilles from 1681 to 1687, at the fort on the Île Sainte-Marguerite from 1687 to 1698, and finally at the Bastille in Paris, where Saint-Mars took up his post as governor on 18 September 1698. The prisoner was placed in a solitary cell in the third chamber of the Bertaudière tower.
He died in the Bastille on 19 November 1703. He was buried the next day in the cemetery of the parish church of Saint-Paul, and his burial certificate recorded his name as “Marchioly” and his age as about forty-five. That is the whole of the documented story, in outline: a man arrested under one name, held in secret for thirty-four years, and buried under another.
The mask
The most famous detail of the story is also the most misleading. The prisoner was not held in an iron mask for thirty-four years. According to the contemporary documents, his face was covered with a mask of black velvet cloth, and only in limited circumstances: when he was travelling between prisons after 1687, and, in his final years at the Bastille, when he went to prayers where other prisoners might see him.
The idea of an iron mask entered the story decades after the prisoner’s death. The writer and philosopher Voltaire, who had himself been imprisoned in the Bastille in 1717, wrote about the prisoner in his Questions sur l’Encyclopédie, published in 1771. Voltaire claimed the mask was made of iron, with a hinged steel chinpiece that allowed the prisoner to eat without removing it — a detail that no contemporary document corroborates. Voltaire also claimed the prisoner was an older, illegitimate brother of Louis XIV. Neither claim has any support in the records from the prisoner’s lifetime.
The candidates
More than fifty candidates, real and hypothetical, have been proposed as the prisoner’s identity. The record supports a short list of serious possibilities and rules out the most famous ones.
The first is the name on the warrant itself: Eustache Dauger. Louvois’s correspondence treats Dauger as a valet, arrested on the minister’s orders for an unknown reason. In 1932 the French historian Maurice Duvivier proposed that the prisoner was Eustache Dauger de Cavoye, a nobleman connected with several political scandals of the late seventeenth century. That identification was disproved in 1953, when previously unpublished family letters showed that Dauger de Cavoye had a documented life elsewhere. The name on the warrant may still have been the prisoner’s real name, or it may have been an alias. The documents do not say.
The second serious candidate is Ercole Antonio Mattioli, an Italian diplomat. Mattioli had been entrusted with the secret negotiation of a 1678 treaty under which the Duke of Mantua would hand the fortress town of Casale to France for 100,000 écus. For much of the nineteenth century, Mattioli was the favoured solution to the mystery, and the burial name “Marchioly” was read as a corruption of “Mattioli.” It is, however, generally agreed today that Mattioli died on the Île Sainte-Marguerite in April 1694, nine years before the masked prisoner died in the Bastille, which makes him an unlikely match.
The most famous candidate of all is the one from fiction. In the 1840s, Alexandre Dumas, in the final part of his D’Artagnan saga, The Vicomte of Bragelonne, made the prisoner the identical twin brother of Louis XIV, hidden away at birth to prevent a rival claim to the throne. Dumas’s version has no documentary support whatsoever. No record from the period supports a secret royal sibling, twin or otherwise.
What the documents actually show
Almost everything known about the prisoner comes from a small body of contemporaneous documents uncovered in the nineteenth century, chiefly the correspondence between Saint-Mars and his superiors in Paris. In 2015, two inventories of Saint-Mars’s goods and papers were found among the records of the Minutier central des notaires in Paris.
Those documents show a prisoner of unusual secrecy, held for thirty-four years, whose face was covered only on certain occasions, and whose jailer guarded him with extraordinary care. They do not show why he was arrested, what he had done, or who he really was. After more than three centuries of research, the identity of the Man in the Iron Mask remains, on the evidence, unknown.
What Is Documented, and What Is Not
Documented: A prisoner arrested under the name “Eustache Dauger” under a warrant dated 19 July 1669 was imprisoned at Pignerol on 24 August 1669 and held for 34 years in the custody of Bénigne Dauvergne de Saint-Mars at Pignerol, Exilles, Île Sainte-Marguerite and the Bastille. He died on 19 November 1703 and was buried the next day under the name “Marchioly,” his age recorded as about 45. Contemporary documents show his face was covered with a black velvet mask only when travelling between prisons or attending prayers in his final years. Voltaire’s 1771 account introduced the iron mask and the claim of a royal brother.
Unverified: The prisoner’s true identity has never been established, and no identity theory is endorsed here. The identification with Ercole Antonio Mattioli is undermined by the accepted view that Mattioli died in April 1694. The identification with Eustache Dauger de Cavoye was disproved in 1953. Voltaire’s iron mask with a hinged chinpiece and Dumas’s identical-twin brother of Louis XIV are unsupported by any contemporary document and should be treated as legend and fiction respectively. The suggestion that Saint-Mars imposed the mask to enhance his own prestige is a historians’ interpretation, not a documented fact.