Jean de Montagu or Jean de Montaigu (c.1363, Paris – Paris, 17 October 1409), was a royal secretary to Charles V, and subsequently an administrator and advisor to Charles VI of France, who became a leading figure in France during the early 15th Century.
She was the daughter of François Cassinel (died 1360), a sergeant in the Royal Army, and great-granddaughter of Bettino Cassinelli, who had immigrated from Italy to Paris.
Through the income derived from his various offices granted to him through the favor of the king, he acquired an immense fortune, and in 1389, Jean bought the lands of Boissy-sous-Saint-Yon and Égly for twelve hundred pounds.,[5] and subsequently inherited and acquired several more estates, including the valuable Château de Montagu.
Being the leading figure of the royal government during the period following the assassination of Louis, the Duke of Orléans, in the ongoing Armagnac-Burgundian Civil War, he developed a very bitter rivalry with the Duke of Burgundy, John the Fearless, who sought to hold the Regency (and the income of the Royal Household) in place of the mentally incapable King Charles, as his father had done.
[6] After an expedited summary trial where he unsuccessfully appealed to the then Burgundian-controlled Parliament a forced confession of treason and other charges upon being subjected to torture, Montagu was beheaded on 17 October 1409 in front of a large crowd in Paris, at the Gibbet of Montfaucon.