RIDOLFI, or RIDOLFO, ROBERTO DI (1531-1612)  , Italian conspirator, belonged to a famous family of Florence, where he was born on the 18th of November 1531 . As a banker he had business connexions with England, and about 1555 he settled in London, where he soon became a person of some importance, and consorted with William Cecil and other prominent men . During the early years of Elizabeth's reign he began to take a more active part in. politics, associating with the discontented Roman Catholics in England and communicating with their friends abroad . In 1570 he set to work on the plot against the queen which is usually associated with his name . His intention was to marry Mary, queen of Scots, to the duke of Norfolk and to place her on the • English throne . With the aid of John Lesley, bishop of Ross, he gained the consent of these high personages to the conspiracy, and then in 1571 he visited the duke of Alva at Brussels, Pius V. at Rome, and Philip II. at Madrid to explain to them his scheme and to gain their active assistance thereto . His messenger, by name Charles Baillie (1542-16.25), was, however, seized at Dover, and in other ways the English government heard of the intended rising . Consequently, Norfolk and Lesley were arrested, the former being cQndemned to' death in January 1572 . Ridolfi, who was then in Paris, could do nothing when he heard this news, and his scheme collapsed . Afterwards he served the pope, but much of his later life was spent in Florence, where he became a senator and where he died on the 18th of February 1612 .