Michel de Castelnau
[3] 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.
[3] 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.
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.
[4][5] He remained with her a year, during which time he made several journeys into England in an attempt to bring about a reconciliation between Mary and Queen Elizabeth.
In the midst of the excited passions of his countrymen, Castelnau, who was a sincere Roman Catholic, maintained a wise self-control and moderation, and by his counsels rendered valuable service to the government.
[6] After Mary married to Lord Darnley in July 1565, he was involved in diplomatic responses to her troubles during the Chaseabout Raid and he visited her at Holyroodhouse.
On this occasion he discovered the project formed by the Prince of Condé and Admiral Coligny to seize and carry off the royal family at Monceaux (1567).
After the battle of St. Denis he was again sent to Germany to solicit aid against the Protestants; and on his return he was rewarded for his services with the post of governor of Saint-Dizier and a company of orderlies.
[3] In 1572 he was sent to England by Charles IX to allay the excitement created by the St. Bartholomew's Day Massacre, and the same year he was sent to Germany and Switzerland.
[10] During this period he used his influence to promote the marriage of the queen with the Duke of Alençon, with a view especially to strengthen and maintain the alliance of the two countries.
[11] A suggestion that Bruno leaked confidential information from the embassy in this period, proposed by the historian John Bossy, has not gained much acceptance.
[13][14] Castelnau's wife Marie had difficult pregnancies and miscarriages and she crossed and recrossed the English channel to see physicians in France, at great expense.
[15] In London, Castelnau de Mauvissière resided at Salisbury Court near Fleet Street or Butcher Row near the Strand.
[21] Mary wrote secret letters in cipher to Castelnau complaining of her bad treatment, in 1581 asking for French money, soldiers, and artillery to be supplied according to the traditional Auld Alliance between England and Scotland.
[22] Frustrated by the apparent lack of support from France, Mary wrote to Castelnau in July 1581 that she could choose to negotiate with Spain instead.
[34] In April 1583, Willam Cecil made a list of Castelnau's previous letters and communications with a Scottish intriguer Archibald Douglas and the favourite of James VI, Esmé Stewart, 1st Duke of Lennox.
[35] A spy using the name "Henry Fagot" offered to bribe Castelnau's secretary to keep Francis Walsingham informed of ciphered letters and the key to the lettre quartallé or cartelée code used in his correspondence with Mary, Queen of Scots.
[40][41] In 2023 around 57 coded letters to Castelnau from Mary, Queen of Scots, were discovered in the Bibliothèque nationale de France and deciphered.
The letters were probably put into cipher by Mary's secretaries Gilbert Curle, Claude Nau, and Jérôme Pasquier, who was variously recorded as master of her wardrobe, a groom of her chamber, a clerk and a household treasurer.
[53] The alleged objective was to facilitate a Spanish invasion of England, assassinate Elizabeth, and put Mary on the English throne.
[58] In August 1584, Castelnau was involved in plans for Mary's secretary Claude Nau to come to London and meet Elizabeth I as a diplomat.
[64] When Castelnau returned to France in September 1585, he wrote to Francis Walsingham that he was sending John Florio to court to thank Elizabeth I for the gifts of silver plate that he had received.
[68] On his return to France he found that his château of La Mauvissière had been destroyed in the civil war;[69] and as he refused to recognize the authority of the League, the Duke of Guise deprived him of the governorship of Saint-Dizier.
But on the accession of Henry IV, the king, who knew his worth, and was confident that although he was a Catholic he might rely on his fidelity, gave him a command in the army, and entrusted him with various confidential missions.
[71] Their grandson, Jacques de Castelnau (1620–1658), distinguished himself in the war against Austria and Spain during the ministries of Richelieu and Mazarin, and died a Marshal of France.
