In the following years, Walsingham became active in soliciting support for the Huguenots in France and developed a friendly and close working relationship with Nicholas Throckmorton, his predecessor as MP for Lyme Regis and a former ambassador to France. By 1569, Walsingham was working with William Cecil to counteract plots against Elizabeth. He was instrumental in the collapse of the Ridolfi plot, which hoped to replace Elizabeth with the Catholic Mary, Queen of Scots. He is credited with writing propaganda decrying a conspiratorial marriage between Mary and Thomas Howard, 4th Duke of Norfolk, and Roberto di Ridolfi, after whom the plot was named, was interrogated at Walsingham's house.