Editing Man in the Iron Mask (section)

===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}}