Plot, and the ciphering process. In his second interview, Pasquier said he "wrote many times in cipher to Mauvissière, the late French ambassador". Nau was in charge of the alphabets or cipher keys, Mary herself kept the letters in cipher. Questioned again, he confessed to ciphering and deciphering letters for Mary and "also having deciphered many other letters written by Monsieur de Mauvissière" and others. After Mary's funeral in August 1587, all three men were released and given passports to leave England. Throckmorton Plot The Throckmorton Plot was revealed late in 1583. Some of Mary's secret letters to Castelnau were carried by Francis Throckmorton to Claude de Courcelles. In the ciphered texts Throckmorton was given the codename or alias Monsieur de la Tour. Another of Castelnau's secretaries, Chérelles, who was trusted by Mary, and a clerk, Laurent Feron, passed copies of Castelnau's correspondence to Walsingham. Chérelles's brother had a place in Mary's household, as treasurer. The wider intrigue discovered by Walsingham involving Throckmorton, and a letter carrier, George More, is known as the Throckmorton Plot. The alleged objective was to facilitate a Spanish invasion of England, assassinate Elizabeth, and put Mary on the English throne.Conyers Read, Bardon Papers (London: Camden Society, 1909), pp. 53-54, 75, 81 The revelation of this plot in November 1583 weakened Castelnau's position as a diplomat. Later, in September 1586, Mary's servant Jérôme Pasquier confessed to writing a letter in cipher for Mary to Castelnau asking him to negotiate a pardon for Francis Throckmorton in a prisoner exchange. Throckmorton was executed. Final months in London In February 1585 Castelnau wrote to Mary's son, James VI. He reported Mary's optimism and her pleasure in her new lodgings at Tutbury Castle. She hoped to be freed and join James in an "association", a joint rule. Castelnau thought he would be sent to Scotland to help reconcile the three nations of Scotland, England, and France. This mission did not take place. His secretary Courcelles (also known as De Preau) came into suspicion for double-dealing in March 1585. He was alleged to have carried letters to the would-be assassin William Parry. He continued to carry letters for Mary after Castelnau's departure from England. Elizabeth heard that Castelnau had banished him for misconduct. 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