Editing Man in the Iron Mask (section)

==Candidates==
{{hatnote|The following sections summarise the main hypotheses debated in reliable sources. See also: [[List of candidates for the Man in the Iron Mask]].}}
In the third edition (2004) of his book on the subject, French historian Jean-Christian Petitfils collated a list of 52 candidates, real or imagined, whose names had been either mentioned as rumours in contemporary documents, or proposed in printed works, between 1669 and 1992.{{sfn|Petitfils|2004|pp=253–257}}

===Contemporary rumours===
A week after Dauger's arrival at Pignerol, Saint-Mars wrote to Louvois (31 August 1669), reporting that the prisoner was rumoured to be a "[[Marshall of France#Louis XIV, 1643–1715|Marshall of France]] or President of ''[[The Fronde (Parlement)|Parlement]]''".{{sfn|Roux-Fazillac|2018|p=105}}{{sfn|Mongrédien|1961|p=185}}{{sfn|Noone|1988|p=257}}{{sfn|Petitfils|2004|p=181}} Eight months later, Saint-Mars informed Louvois (12 April 1670) that he initiated some of these rumours himself, when asked about the prisoner: "I tell them tall tales to make fun of them."{{sfn|Roux-Fazillac|2018|p=105}}{{sfn|Mongrédien|1961|p=186}}{{sfn|Noone|1988|p=153}}{{sfn|Petitfils|2004|p=182}}

A few months after Dauger was relocated to his new prison cell at the Île Sainte-Marguerite Fort in January 1687, Saint-Mars wrote to Louvois about the latest rumours (3 May 1687): "Everyone tries to guess who my prisoner might be."{{sfn|Roux-Fazillac|2018|p=116}}{{sfn|Laloy|2018|p=16}}{{sfn|Mongrédien|1961|pp=117–118}}{{sfn|Petitfils|2004|p=66}}{{sfn|Noone|1988|p=265}} On 4 September 1687, the ''Nouvelles Écclésiastiques'' published a letter by Nicolas Fouquet's brother Louis, quoting a statement made by Saint-Mars: "All the people that one believes dead are not", a hint that the prisoner might be the [[François de Vendôme, duc de Beaufort|Duke of Beaufort]].{{sfn|Azéma|1963|p=150}}{{sfn|Brugnon|1989|p=4}}{{sfn|Noone|1988|pp=264–266}}{{sfn|Petitfils|2004|pp=103–104}} Four months later, Saint-Mars reiterated this "rumour" in writing to Louvois (8 January 1688), adding: "(...) others say that he is a son of the late [[Oliver Cromwell|Cromwell]]".{{sfn|Mongrédien|1961|p=120}}{{sfn|Noone|1988|pp=59–67, 125, 132, 147}}{{sfn|Petitfils|2004|pp=33, 191–192, 202, 215, 218, 220}}{{sfn|Fréron|1768|p=189}}

===English milord===
On 10 October 1711, King Louis XIV's sister-in-law, [[Elizabeth Charlotte, Princess Palatine]], sent a letter to her aunt, [[Sophia of Hanover|Sophia, Electress of Hanover]], stating that the prisoner had "two [[musketeers]] at his side to kill him if he removed his mask". She described him as very devout, and stated that he was well treated and received everything he desired.{{sfn|Mongrédien|1961|p=31}} In another letter sent less than two weeks later, on 22 October, she added having just learnt that he was "an English milord connected with the affair of the [[James FitzJames, 1st Duke of Berwick|Duke of Berwick]] against [[William III of England|King William III]]."{{sfn|Mongrédien|1961|p=31}} The Princess was clearly reporting rumours she had heard at court.{{sfn|Mongrédien|1961|pp=31–33, 236}}{{sfn|Bodemann|1891|pp=288–293}}

===King's relative===
Some of the most enduring theories about the prisoner's identity, outlined in the sections below, assume that he was a relative of Louis XIV, because of the importance attached to secrecy during his incarceration which, in turn, fed the legend that he must have been one of the most important persons in the realm.{{sfn|Mongrédien|1961|p=42}} These theories emerged during the 1700s, long before historians were able to consult the archives revealing that the prisoner was "only a valet",{{sfn|Mongrédien|1961|pp=181–182}} imprisoned for "what he was employed to do", and for "what he knew".{{sfn|Mongrédien|1961|p=190}} These early theories arose solely from their author's imagination, and boosted the romantic appeal of a sensational elucidation of the enigma.{{sfn|Mongrédien|1961|pp=40–52}} Historians such as Mongrédien (1952) and Noone (1988), however, pointed out that the solution whereby Louis XIV is supposed to have had an illegitimate brother&mdash;whether older, twin, or younger&mdash;does not provide a credible explanation, for example, on how it would have been possible for Queen [[Anne of Austria]] to conceal a pregnancy throughout its full course and bear, then deliver, a child in secret.{{sfn|Mongrédien|1961|p=51}}{{sfn|Noone|1988|p=45}} Mongrédien concluded that "historians cannot give it the slightest credence."{{sfn|Mongrédien|1961|p=52}}

====King's illegitimate son====
In 1745, an anonymous writer published a book in Amsterdam, ''Mémoires pour servir à l'Histoire de la Perse'', romanticising life at the French Court in the form of Persian history. Members of the royal family and locations were given fictitious Persian names,{{sfn|Mongrédien|1961|p=33}} and their key was published in the book's third edition (1759).{{sfn|Noone|1988|p=51}} In this tale, Louis XIV's illegitimate son, [[Louis, Count of Vermandois]], is alleged to have struck his half-brother, [[Louis, Grand Dauphin]], causing the King to banish him to life imprisonment, first at the Île Sainte-Marguerite and later at the Bastille. He was made to wear a mask whenever he was to be seen or attended to, when sick or in other circumstances.{{sfn|Anonymous|1745}}{{sfn|Mongrédien|1961|pp=33–37}}{{sfn|Noone|1988|pp=51–54}} The theory of Vermandois as the prisoner in the mask was later mentioned by [[Henri Griffet]], in 1769, as having circulated during the reign of Louis XIV, therefore long before 1745.{{sfn|Griffet|1769|p=323}}{{sfn|Mongrédien|1961|p=236}}

In reality, there are no historical records of gossip confirming that Vermandois ever struck the Grand Dauphin.{{sfn|Mongrédien|1961|pp=37–38}}{{sfn|Noone|1988|p=54}} In the memoirs of Louis XIV's first cousin, the [[Anne Marie Louise d'Orléans, Duchess of Montpensier|Duchess of Montpensier]], there is mention of Vermandois having displeased the King for taking part in orgies in 1682, and being temporarily banished from court as a result. After promising to mend his way, he was sent&mdash;soon after his 16th birthday&mdash;to join the army in [[Courtrai]] during the [[War of the Reunions]] (1683–84), in early November 1683. He distinguished himself in the battle line, but died of a fever during the night of 17 November. The King was reported to be deeply affected by his son's death, and Vermandois' sister, [[Marie Anne de Bourbon]], was inconsolable while their mother, [[Louise de La Vallière]], sought solace in endless prayer at her [[Carmelites]] [[Couvent des Carmélites du faubourg Saint-Jacques|convent]] in Paris.{{sfn|Mongrédien|1961|pp=38–39}}{{sfn|Noone|1988|p=51}}

====King's elder brother====
During his two sojourns in the Bastille in 1717–18 and 1726,{{efn|name=voltaire}} Voltaire became aware of the traditions and legends circulating among the staff at the fortress.{{sfn|Mongrédien|1961|pp=40–41}} On 30 October 1738, he wrote to the [[Jean-Baptiste Dubos|Abbé Dubos]]: "I am somewhat knowledgeable about the adventure of the Man in the Iron Mask, who died at the Bastille; I spoke to people who had served him."{{sfn|Mongrédien|1961|pp=41, 237}} In the second edition of his {{lang|fr|Questions sur l'Encyclopédie}} (1771), Voltaire claimed that the prisoner was an illegitimate first son of Anne of Austria and an unknown father, and therefore an older half-brother of Louis XIV.{{sfn|Mongrédien|1961|pp=47–48}} This assertion was partly based on the historical fact that the birth of Louis XIV on 5 September 1638 had come as a surprise: since [[Louis XIII]] and Anne of Austria had been childless for 23 years, it was believed they were unable to conceive, despite evidence to the contrary of the Queen's well-known miscarriages.{{efn|name=annemisc}}{{sfn|Mongrédien|1961|pp=47–49}} In fact, the royal couple had been living for years in mutual distrust and had become estranged since the mid-1620s. Furthermore, in August 1637, the Queen had been found guilty of treasonable correspondence with Spain and had been placed under house arrest at the [[Louvre Palace]].{{sfn|Noone|1988|p=42}} However, contemporary accounts nonetheless indicate that the royal couple shared a bed and conceived the future Louis XIV, either in early December 1637{{efn|name=dec1637}} or, as historians deem more likely, sometime during the previous month.{{efn|name=nov1637}}{{sfn|Kleinman|1993|p=194}}{{sfn|Mansel|2022|p=17}} The Queen's pregnancy was made public on 30 January 1638.{{sfn|Mansel|2022|p=17}}

Based on the assumption that the royal couple were unable to conceive, Voltaire theorised that an earlier, secret birth of an illegitimate child persuaded the Queen that she was not infertile, in turn prompting [[Cardinal Richelieu]] to arrange an outing during which the royal couple had to share a bed, which led to the birth of Louis XIV.{{sfn|Voltaire|1770–1771}}{{sfn|Carra|1789|pp=315–321}}{{sfn|Craufurd|1790|pp=254–356}}{{sfn|Mongrédien|1961|pp=40–49}}

The theme of an imagined elder brother of Louis XIV resurfaced in 1790, when French historian Pierre-Hubert Charpentier asserted that the prisoner was an illegitimate son of Anne of Austria and [[George Villiers, 1st Duke of Buckingham]], supposedly born in 1626, two years before the latter's death.{{sfn|Charpentier|Manuel|1790|pp=140–162}}{{sfn|Mongrédien|1961|p=50}}{{sfn|Noone|1988|pp=43–45}} Louis XIV was presumed to have had this elder brother imprisoned upon the Queen's death in 1666. According to Charpentier, this theory had originated with a certain Mademoiselle de Saint-Quentin, a mistress of the [[Louis François Marie Le Tellier|Marquess of Barbezieux]], son of Louvois and his successor as War Minister to Louis XIV in 1691.{{sfn|Mongrédien|1961|p=50}} A few days before his sudden death on 5 January 1701, Barbezieux had told her the secret of the prisoner's identity, which she disclosed publicly to several people in [[Chartres]] towards the end of her life in the mid-1700s. Charpentier also stated that Voltaire had heard this version in [[Geneva]], but chose to omit Buckingham's name when he began to develop his own variant of this theory in the first edition of ''[[The Age of Louis XIV]]'' (1751),{{sfn|Charpentier|Manuel|1790|pp=140–162}} finally revealed in full in {{lang|fr|Questions sur l'Encyclopédie}} (1771).{{sfn|Charpentier|Manuel|1790|pp=140–162}}

====King's twin brother====
Many authors supported the theory of the prisoner being a twin brother of King Louis XIV: [[Michel de Cubières]] (1789), [[Jean-Louis Giraud Soulavie|Jean-Louis Soulavie]] (1791), [[Emmanuel, comte de Las Cases|Las Cases]] (1816), [[Victor Hugo]] (1839), Alexandre Dumas (1840), Paul Lecointe (1847), and others.{{sfn|Mongrédien|1961|p=51}} 
<!-- Aligned with this theory, a thorough examination of the French Kings' genealogy shows many twin births, in the [[Capetian dynasty]], as well as in the [[House of Valois]], the [[House of Bourbon]], and the [[House of Orléans]].{{sfn|Kermabon|1998}}
-->

In a 1965 essay, ''Le Masque de fer'' (revised in 1973 under the title ''[[Le secret du Masque de Fer]]''), French novelist and playwright [[Marcel Pagnol]], proposing his hypothesis in particular on the circumstances of Louis XIV's birth, claimed that the Man in the Iron Mask was indeed a twin brother, but born second, who would have been hidden in order to avoid any dispute over the throne holder.{{sfn|Pagnol|1973|pp=19–22}} At the time, there was a controversy over which one of twins was the elder: the one born first, or the one born second, who was then thought to have been conceived first.{{sfn|Pagnol|1973|pp=289–290, 334}}

Historians who reject this hypothesis (including [[:fr:Jean-Christian Petitfils|Jean-Christian Petitfils]]) highlight the conditions of childbirth for the queen: it usually took place in the presence of multiple witnesses—the main court's figures. According to Pagnol, immediately after the birth of the future Louis XIV at 11 a.m. on 5 September 1638, Louis XIII took his whole court (about 40 people) to the [[Château de Saint-Germain-en-Laye|''Château de Saint-Germain'']]'s chapel to celebrate a ''[[Te Deum]]'' in great pomp,{{sfn|Pagnol|1973|pp=19–22}} contrary to the common practice of celebrating it several days before childbirth.{{sfn|Dumont|1739}} Pagnol contends that the court's removal to this ''Te Deum'' had been rushed to enable the queen to deliver the second twin in secret and attended only by the midwife.{{sfn|Pagnol|1973|pp=19–22}}

Pagnol's solution&mdash;combining earlier theories by [[Jean-Louis Giraud Soulavie|Soulavie]] (1790),{{sfn|Soulavie|1790}} [[Andrew Lang]] (1903),{{sfn|Lang|2002}} [[Arthur Barnes (monsignor)|Arthur Barnes]] (1908),{{sfn|Barnes|1908}} and Edith Carey (1924){{sfn|Carey|1924}}&mdash;speculates that this twin was born a few hours after Louis XIV and grew up on the Island of [[Jersey]] under the name [[James de la Cloche]], believing himself to be an illegitimate son of [[Charles II of England|Charles II]]. During a hypothetical, secret meeting in January 1669, Charles is assumed to have recognised the twin for his resemblance to the French king and revealed to him his true identity.{{sfn|Pagnol|1973|pp=330–334}} Shortly thereafter, the twin would supposedly have adopted the new identity of "Martin" as a valet to [[Roux de Marcilly]], with whom he conspired against Louis XIV, which led to his arrest in Calais in July 1669.{{sfn|Pagnol|1973|pp=137–165}} Historically, however, the real valet Martin (distinct from Pagnol's reinterpreted "Martin") could not have become "Eustache Dauger" because he had fled to London when the Roux conspiracy failed; this is well known because his extradition from England to France had at first been requested by Foreign Minister [[Hugues de Lionne]] on 12 June 1669, but subsequently cancelled by him on 13 July.{{sfn|Noone|1988|p=187}} Pagnol explained this historical fact away by claiming, without any evidence, that "Martin" must have been secretly abducted in London in early July and transported to France on 7 or 8 July, and that the extradition order had therefore been cancelled because it was no longer necessary, its objective having already been achieved.{{sfn|Pagnol|1973|pp=155–156}}

====King's younger brother====
In 1791, Jean Baptiste De Saint-Mihiel proposed that the prisoner was an illegitimate younger brother of Louis XIV, fathered by [[Cardinal Mazarin]].{{sfn|Mongrédien|1961|p=51}} This theory was based on the fact, mentioned by Voltaire in {{lang|fr|Questions sur l'Encyclopédie}} (1771), that the prisoner had told his doctor that he "believed himself to be about 60 years old", a few days before his death in 1703. De Saint-Mihiel extrapolated that the prisoner was therefore born around 1643, and could therefore only be a younger brother to the King, born in 1638.{{sfn|Petitfils|2004|pp=224–225}} It is a historical fact that, four days after Louis XIII's death on 14 May 1643, the Queen was declared Regent and appointed Mazarin as her chief minister and head of government that evening.{{sfn|Dethan|1959|pp=50–51}} Mazarin was soon believed to be her lover, and even her secret [[Morganatic marriage|morganatic husband]].{{sfn|Treasure|1984|pp=216–217}} The theory of the prisoner being an imagined, younger son of the Queen and Mazarin was rekindled in 1868 by Charles-Henri, baron de Gleichen.{{sfn|Gleichen|1868||pp=46–50}}{{sfn|Mongrédien|1961|p=51}}

====King's father====
In 1955, Hugh Ross Williamson argued that the Man in the Iron Mask was the natural father of Louis XIV. According to this theory, the "miraculous" birth of Louis XIV in 1638 would have come after Louis XIII had been estranged from his wife Anne of Austria for 14 years.{{sfn|Williamson|2002|p=245}}

The theory then suggests that Cardinal Richelieu had arranged for a substitute, probably an illegitimate grandson of [[Henry IV of France|Henry IV]],{{sfn|Williamson|2002|p=247}} to become intimate with the queen and father an heir in the king's stead. At the time, the [[heir presumptive]] was Louis XIII's brother [[Gaston, Duke of Orléans]], who was Richelieu's enemy. If Gaston became king, Richelieu would quite likely have lost both his job as minister and his life, and so it was in his best interests to thwart Gaston's ambitions.{{sfn|Williamson|2002|p=246}}

Supposedly, the substitute father then left for the [[New France|Americas]] but returned to France in the 1660s with the aim of extorting money for keeping his secret and was promptly imprisoned. This theory would explain the secrecy surrounding the prisoner, whose true identity would have destroyed the legitimacy of Louis XIV's claim to the throne had it been revealed.{{sfn|Williamson|2002|pp=247–248}}

This theory had been suggested by British politician [[Hugh Cecil, 1st Baron Quickswood]], who nonetheless added that the idea has no historical basis and is entirely hypothetical.{{sfn|Williamson|2002|p=245}} Williamson held that: "to say it is a guess with no solid historical basis is merely to say that it is like every other theory on the matter, although it makes more sense than any of the other theories. There is no known evidence that is incompatible with it, even the age of the prisoner, which Cecil had considered a weak point;{{sfn|Williamson|2002|pp=249–251}} and it explains every aspect of the mystery."{{sfn|Williamson|2002|p=245}}  His time spent as a valet to another prisoner renders this idea doubtful, however.{{efn|name=valet}}

===Italian diplomat===
Another candidate, much favoured in the 1800s, was Fouquet's fellow prisoner Count Ercole Antonio Mattioli ({{aka}} Matthioli). He was an Italian diplomat who acted on behalf of the debt-ridden [[Charles IV, Duke of Mantua]] in 1678, in selling [[Casale Monferrato|Casale]], a strategic fortified town near the border with France. A French occupation would be unpopular, so discretion was essential, but Mattioli leaked the details to France's Spanish enemies after pocketing his commission once the sale had been concluded, and they made a bid of their own before the French forces could occupy the town. Mattioli was kidnapped by the French and thrown into nearby Pignerol in April 1679. The French took possession of Casale two years later.{{sfn|Noone|1988}}

[[George Agar-Ellis]] reached the conclusion that Mattioli was the Man in the Iron Mask when he reviewed documents extracted from French archives in the 1820s.{{sfn|Agar-Ellis|1826}} His book, published in English in 1826, was translated into French and published in 1830. German historian Wilhelm Broecking came to the same conclusion independently seventy years later. [[Robert Chambers (journalist)|Robert Chambers]]' ''[[Chambers Book of Days|Book of Days]]'' supports the claim and places Matthioli in the Bastille for the last 13 years of his life. Since that time, letters sent by Saint-Mars, which earlier historians missed, indicate that Mattioli was held only at Pignerol and Sainte-Marguerite and was not at Exilles or the Bastille and, therefore, it is argued that he can be discounted.{{sfn|Lincoln ''Timewatch'', 1988}}

===French general===
{{See also|Great Cipher#The Man in the Iron Mask}}

In 1890, Louis Gendron, a French military historian, came across some coded letters and passed them on to [[Étienne Bazeries]] in the French Army's cryptographic department. After three years, Bazeries managed to read some messages in the [[Great Cipher]] of Louis XIV. One of them referred to a prisoner and identified him as General Vivien de Bulonde. One of the letters written by Louvois made specific reference to de Bulonde's crime.{{sfn|Noone|1988|p=86}}

At the [[Siege of Cuneo (1691)|Siege of Cuneo]] in 1691, Bulonde was concerned about enemy troops arriving from Austria and ordered a hasty withdrawal, leaving behind his munitions and wounded men. Louis XIV was furious and in another of the letters specifically ordered him "to be conducted to the fortress at Pignerol where he will be locked in a cell and under guard at night, and permitted to walk the battlements during the day with a 330 309." It has been suggested that the 330 stood for ''masque'' and the 309 for full stop. However, in 17th-century French ''avec un masque'' would mean "in a mask".{{sfn|Noone|1988|p=87}}

Some believe that the evidence of the letters means that there is now little need for an alternative explanation of the man in the mask. Other sources, however, claim that Bulonde's arrest was no secret and was actually published in a newspaper at the time. Bulonde was released by order of the king on 11 December 1691.{{sfn|de Grandmaison 1894; pp. 3–4}} His death is also recorded as happening in 1709, six years after that of the man in the mask.{{sfn|Noone|1988|p=88}}

===Son of Charles II===
In 1908, Monsignor [[Arthur Barnes (monsignor)|Arthur Barnes]] proposed that the prisoner was [[James de la Cloche]], the alleged illegitimate son of the reluctant Protestant Charles II of England, who would have been his father's secret intermediary with the Catholic court of France.{{sfn|Barnes|1908}} One of Charles's confirmed illegitimate sons, the [[James Scott, 1st Duke of Monmouth|Duke of Monmouth]], has also been proposed as the man in the mask. A Protestant, he led [[Monmouth Rebellion|a rebellion]] against his uncle, the Catholic [[James II of England|King James II]]. The rebellion failed and Monmouth was executed in 1685. However, in 1768, a writer named Saint-Foix claimed that another man was executed in his place and that Monmouth became the masked prisoner, it being in Louis XIV's interests to assist a fellow Catholic like James, who would not necessarily want to kill his own nephew. Saint-Foix's case was based on unsubstantiated rumours and allegations that Monmouth's execution was faked.{{sfn|Noone|1988}}

===Eustache Dauger de Cavoye===
In his letter to Saint-Mars announcing the imminent arrival of the prisoner who would become the Man in the Iron Mask, Louvois gave his name as "Eustache Dauger". Historically, this was deemed to be a prison pseudonym, and a succession of historians therefore attempted to find out the prisoner's real identity. Among them, Maurice Duvivier (1932) wondered if, instead, "Eustache Dauger" might not be the real name of a person whose life and history could be traced; he therefore combed the archives for surnames such as Dauger, Daugers, d'Auger, d'Oger, d'Ogiers and similar forms. He discovered the family of François d'Oger de Cavoye, a captain of Cardinal Richelieu's guard of musketeers, who was married to Marie de Sérignan, a [[lady-in-waiting]] at the court of Louis XIV's mother, Queen Anne of Austria. François and Marie had 11 children, of whom six boys and three girls survived into adulthood.{{sfn|Mongrédien|1961|p=211}}{{sfn|Noone|1988|pp=212–213}}

Their third son was named Eustache, who signed his name as "Eustache Dauger de Cavoye". He was born on 30 August 1637 and baptised on 18 February 1639.{{efn|name=cavatars}} When his father and  two eldest brothers were killed in battle, Eustache became the nominal head of the family. In his 1932 book, Duvivier published evidence that this man had been involved in scandalous and embarrassing events, first in 1659, then again in 1665,{{sfn|Mongrédien|1961|p=211}}{{sfn|Noone|1988|pp=212–213}} and speculated that he had also been linked with ''[[Affair of the Poisons|l'Affaire des Poisons]]''.{{sfn|Noone|1988|pp=222–228}}

====Disgrace====
In April 1659, Eustache Dauger de Cavoye and others{{efn|name=roissy}} were invited by the [[Louis Victor de Rochechouart de Mortemart|duke of Vivonne]] to an Easter weekend party at the castle of [[Roissy-en-Brie]]. By all accounts, it was a debauched affair of merry-making, with the men involved in all sorts of sordid activities, including attacking an elderly man who claimed to be Cardinal Mazarin's attorney. It was also rumoured, among other things, that a [[black mass]] was enacted and that a pig was baptised as "[[Carp]]" in order to allow them to eat pork on Good Friday.{{sfn|Mongrédien|1961|p=212}}{{sfn|Noone|1988|pp=213–215}}

When news of these events became public, an inquiry was held and the various perpetrators jailed or exiled. There is no record as to what happened to Dauger de Cavoye but, in 1665, near the [[Château de Saint-Germain-en-Laye]], he allegedly killed a young [[Page (occupation)|page boy]] in a drunken brawl involving the Duc de Foix. The two men claimed that they had been provoked by the boy, who was drunk, but the fact that the killing took place close to where Louis XIV was staying at the time meant that this crime was deemed a personal affront to the king and, as a result, Dauger de Cavoye was forced to resign his [[French Royal Army|commission]]. His mother died shortly afterwards. In her will, written a year earlier, she passed over her eldest surviving sons Eustache and Armand, leaving the bulk of the estate to their younger brother Louis. Eustache was restricted in the amount of money to which he had access, having built up considerable debts, and left with barely enough for "food and upkeep".{{sfn|Noone|1988|p=216}}

====Affair of the Poisons====
{{main|Affair of the Poisons}}
In his 1932 book, Duvivier also linked Eustache Dauger de Cavoye to the [[Poison affair|Affair of the Poisons]], a notorious scandal of 1677–1682 in which people in high places were accused of being involved in black mass and poisonings. An investigation had been launched, but Louis XIV instigated a cover-up when it appeared that his mistress [[Françoise-Athénaïs, marquise de Montespan|Madame de Montespan]] was involved.{{sfn|Noone|1988|p=225}} The records show that, during the inquiry, the investigators were told about a surgeon named Auger, who had supplied poisons for a black mass that took place before March 1668. Duvivier became convinced that Dauger de Cavoye, disinherited and short of money, had become Auger, the supplier of poisons, and subsequently "Eustache Dauger".{{sfn|Noone|1988|pp=222–228}}

In a letter sent by Louvois to Saint-Mars on 10 July 1680, a few months after Fouquet's death in prison while "Eustache Dauger" was acting as his valet, the minister adds a note in his own handwriting, asking how it was possible that Dauger had made certain objects found in Fouquet's pockets—which Saint-Mars had mentioned in a previous correspondence, now lost—and "how he got the drugs necessary to do so".{{sfn|Mongrédien|1961|p=194}}{{sfn|Noone|1988|p=220}} Duvivier suggested that Dauger had poisoned Fouquet as part of a complex power struggle between Louvois and his rival [[Jean-Baptiste Colbert|Colbert]].{{sfn|Noone|1988|p=221}}

====Dauger de Cavoye in prison at Saint-Lazare====
In 1953, however, French historian Georges Mongrédien published historical documents{{efn|name=cavoye}} confirming that, in 1668, Eustache Dauger de Cavoye was already held at the [[Prison Saint-Lazare]] in Paris—an asylum, run by monks, which many families used in order to imprison their "[[black sheep#Idiomatic usage|black sheep]]"—and that he was still there in 1680,{{sfn|Mongrédien|1961|p=220}} at the same time that "Eustache Dauger", was in custody in Pignerol, hundreds of miles away in the south. These documents include a letter dated 20 June 1678, full of self-pity, sent by Dauger de Cavoye to his sister, the Marquise de Fabrègues,{{efn|name=sarret}} in which he complains about his treatment in prison, where he had already been held "for more than 10 years", and how he was deceived by their brother Louis and by Clérac, their brother-in-law and the manager of Louis's estate.{{sfn|Mongrédien|1953|pp=56–57}}

Dauger de Cavoye also wrote a second letter, this time to the King but undated, outlining the same complaints and requesting his freedom.{{sfn|Mongrédien|1953|pp=57–58}} The best the King would do, however, was to send a letter to the head of Saint-Lazare on 17 August 1678,{{efn|name=stlazare}} telling him that "M. de Cavoye should have communication with no one at all, not even with his sister, unless in your presence or in the presence of one of the priests of the mission". The letter was signed by the King and Colbert.{{sfn|Noone|1988|pp=231–234}} A poem written by Louis-Henri de Loménie de Brienne, an inmate in Saint-Lazare at the time, indicates that Eustache Dauger de Cavoye died as a result of heavy drinking in the late 1680s. Historians consider all this proof enough that he was not involved in any way with the man in the mask.{{sfn|Noone|1988|p=233}}{{sfn|Lincoln ''Timewatch'', 1988}}

===Valet===
In 1890, French historian [[Jules Lair]] published an extensive, two-volume biography of Nicolas Fouquet in which he relates Eustache Dauger's arrival at Pignerol in August 1669,{{sfn|Lair|1890|p=453}} his subsequent role as Fouquet's valet, and their secret interactions with Lauzun.{{sfn|Lair|1890|p=454}} Lair believed that "Eustache Dauger" was the new prisoner's real name, that he was French, [[Roman Catholic (term)|catholic]] and a professional valet who had been employed for a specific task which was never clarified: "he was probably one of these men tasked with a shady mission&mdash;such as the removal of documents or kidnapping, or perhaps worse&mdash;and whose silence is secured by death or imprisonment once the deed is done."{{sfn|Lair|1890|p=454}} Lair also conjectured an explanation for Louvois's obsessive insistence that Dauger and Lauzun should be kept apart at all times, by reference to the fact that Dauger was arrested near Dunkirk during the negotiations of the [[Secret Treaty of Dover]], in which Lauzun had also participated. Lair asserted that the two men knew each other or, at the very least, had been aware of each other.{{sfn|Lair|1890|pp=454–455}}

In 2016, American historian Paul Sonnino speculated that Eustache Dauger could have been a valet of Cardinal Mazarin's treasurer, Antoine-Hercule Picon. A native of Languedoc, Picon, upon entering the service of Colbert after Mazarin's death, might have picked up a valet from Senlis, where the name "Dauger" abounds. In his book, Sonnino asserts that Mazarin led a double life, "one as a statesman, the other as a loan shark", and that one of the clients he embezzled was [[Henrietta Maria]], the widow of [[Charles I of England]]. According to Sonnino's theory, Louis XIV was complicit and instructed his ambassador in England to stonewall Charles II over the return of his parents' possessions. In 1669, however, Louis wanted to enlist Charles in a war against the Dutch and therefore worried about the subject of Mazarin's estate entering into the negotiations. Sonnino concludes by stating that Eustache Dauger, who might have been Picon's valet, was arrested and incarcerated for revealing something about the disposition of Mazarin's fortune, and that this is why he was threatened with death if he disclosed anything about his past.{{sfn|Sonnino|2016|pp=155–156}}{{sfn|Deamer|2016}}{{sfn|Egnal|2021}}

In 2021, British historian Josephine Wilkinson mentioned the theory proposed by French historian  Bernard Caire in 1987, whereby "Eustache" was not the prisoner's first name but his real surname. Since French historian Jean-Christian Petitfils had earlier asserted that "Dauger" was a misspelling of "Danger" (or d'Angers), Caire suggested that this appellation was used to indicate the prisoner originated from the town of [[Angers]].{{efn|name=danger}}{{sfn|Wilkinson|2021|pp=238–239}} Wilkinson also supported the theory proposed by Petitfils&mdash;and by Jules Lair in 1890&mdash;that, as a valet (perhaps to [[Henrietta of England]]), this "Eustache" had committed some indiscretion which risked compromising the relations between Louis XIV and Charles II at a sensitive time during the negotiations of the Secret Treaty of Dover against the [[Dutch Republic]]. In July 1669, Louis had suddenly and inexplicably fallen out with Henrietta and, since the two had previously been very close, it did not go unnoticed. Wilkinson therefore suggested a link between this event and this valet's arrest in Calais later that month.{{sfn|Wilkinson|2021|pp=247–253}}