Short answers, pulled from the story.
Antoine de Castelnau was a French diplomat and bishop who served as ambassador to England and Spain during the reign of Francis I. He held the position of Bishop of Tarbes from 1534 until his death in 1539. He is notable for his diplomatic intelligence work and for his connection to accounts of Anne Boleyn's trial and execution.
Antoine de Castelnau served as Francis I's ambassador to the court of Henry VIII from the 26th of June 1535 until 1537. He succeeded Charles de Solier, comte de Morette, and was himself succeeded by Louis de Perreau, Sieur de Castillon.
Castelnau discovered that Charles V had secretly proposed a marriage between Princess Mary, daughter of Henry VIII, and Dom Luis, Charles's brother-in-law, with the Duchy of Milan offered as part of the arrangement. He reported these intrigues back to Francis I.
Lancelot de Carle was the secretary of Antoine de Castelnau and an eye-witness to Anne Boleyn's trial and execution. While living under Castelnau's roof, de Carle wrote a controversial poem detailing Anne Boleyn's life and what he had seen and heard during her downfall.
Antoine de Castelnau was the son of Louis de Castelnau, baron of Castelnau, Miremont, Buanes and Bats, and Susanne de Gramont. His brother, Louis de Castelnau, Abbot of Divielle, succeeded him as Bishop of Tarbes in 1540, a year after Antoine's death.
Antoine de Castelnau died in Toledo, Spain, in 1539. He had been appointed ambassador to Spain after his tenure in England and died there while still in service.