Michel de Castelnau, Sieur de la Mauvissière (c. 1520–1592) was a French soldier and diplomat, ambassador to Queen Elizabeth. He wrote a memoir covering the period between 1559 and 1570. Life He was born in La Mauvissière (now part of Neuvy-le-Roi, Indre-et-Loire), Touraine about 1520. He was a son of Jean de Castelnau and Jeanne Dusmesnil, one of a family of nine children. His grandfather, Pierre de Castelnau, had been Equerry (Master of the Horse) to Louis XII. Endowed with a clear and penetrating intellect and remarkable strength of memory, he received a careful education, capped off with travels in Italy and a long stay at Rome. He then spent some time in Malta and afterwards entered the army. His first acquaintance with war was in the campaigns of the French in Italy. His abilities and his courage won him the friendship and protection of Charles, Cardinal of Lorraine, who took him into his service. In 1557 a command in the navy was given to him, and the cardinal proposed to get him knighted. This, however, he declined, and then rejoined the French army in Picardy. Various delicate missions requiring tact and discretion were entrusted to him by the Constable, Anne de Montmorency, and these he discharged so satisfactorily that he was sent by the king, Henry II, to Scotland with dispatches for Mary of Guise, the mother of Mary, Queen of Scots, who was betrothed to the Dauphin (afterwards Francis II). From Scotland he passed into England in 1559, and treated with Queen Elizabeth respecting her claims on Calais, a settlement of which was effected at the congress of Le Cateau-Cambrésis. He was next sent as ambassador to the princes of Germany, for the purpose of prevailing upon them to withdraw their favor from the Protestants. This embassy was followed by missions to Margaret of Austria, governess of the Netherlands, to Savoy, and then to Rome, to ascertain the views of Pope Paul IV in regard to France. Paul having died just before his arrival, Castelnau used his influence in favor of the election of Pius IV. Returning to France, he once more entered the navy, and served under his former patron. It was his good fortune, at Nantes, to discover the earliest symptoms of the Conspiracy of Amboise, which he immediately reported to the government. After the death of Francis II in December 1560, he accompanied Mary, Queen