Further evidence of Spanish ill will was provided in March 1571, with the uncovering of a plot which involved the King of Spain and the Pope, along with the Queen of Scots and the Duke of Norfolk. The arch-conspirator who was trying to knit these disparate elements together was Ridolfi, and his idea was that Norfolk should call on the English catholics to rise in rebellion, seize Elizabeth and free Mary from captivity, at the same time as a Spanish expeditionary force landed on the cast coast. It is most unlikely that the plot would ever have succeeded, but Cecil discovered what was afoot and grasped the opportunity to remove Norfolk, once and forever, from the political scene. The Duke was arrested, put on trial for high treason, and found guilty. Six months later, after the Queen's doubts and hesitations had been overcome, he was executed on Tower Hill.

A plot to overthrow the queen had already galvanised England in 1571-2, centred yet again on that arch-conspirator Roberto Ridolfi. Within days of the Duke of Norfolk's release from the Tower in August 1570 and into confinement at Howard House in London, the audacious Florentine had visited him secretly. A visitor with such a poor sense of timing could hardly have been less welcome. Ridolfi asked the apprehensive Norfolk to write to the Duke of Alva, the Spanish captain-general in the Netherlands, seeking funds for the imprisoned Mary Queen of Scots. Wisely, Norfolk shunned him - "I began to mislike him," he said much later, and "sought ways to shift me from him."

It was a rare moment of perception, for this double agent was eventually the deceitful means used to bring Norfolk to the scaffold. Despite all that he had suffered, Norfolk's other nemesis, Mary Queen of Scots, was still keen to marry him and to embroil him in a new, dangerous conspiracy. She wrote to him on 31 January 1571, encouraging his escape from house arrest - "as she would do herself, notwithstanding any danger" - in order that they could be married. One can imagine Norfolk's incredulous expression when he read her wholly unrealistic letter, its contents, if not the stuff of daydreams, certainly of rampant self-deception.

The Scottish queen's fantasies aside, the duke's final downfall was triggered by the arrest of Charles Bailly, a young Fleming who had entered Mary's service in 1564 and later worked for John Leslie, Bishop of Ross, her agent in London. Burghley's agents in Dover had detained him in early April 1571 after discovering he was carrying books and letters from English exiles and had no valid passport. Two of the communications, "hid behind his back secretly", were addressed to the bishop and had been dictated to Bailly by the ubiquitous Ridolphi in Brussels. The prisoner was brought to London and held in the Beauchamp Tower in the Tower of London, where grim inscriptions on the walls of a secondfloor room, carved by him in the utter despair of imprisonment, survive to this day. They include some painfully true words, and Bailly's woeful sentiments are justified by the treatment he received at the hands of his torturers in the Tower. A brief session on the rack - a fiendish machine that stretched the body and agonisingly dislocated the joints' - plus the threat of further such treatment to come compelled the prisoner to make some startling admissions. He admitted that Ridolfi had left England on 25 March with personal appeals from Mary to the Duke of Alva in the Low Countries, his master - King Philip II - and the Pope to organise and fund an invasion of England. The aim was to overthrow Elizabeth, crown the Scottish queen and re-establish Catholicism as the state religion. Earlier that month, Ridolfi had revisited Norfolk at Howard House in Charterhouse Square, leaving a document with him that outlined the invasion plans and listed some forty luminaries in England who secretly supported Mary, each name identified by a number for use in ciphered correspondence.

I am given secretly to understand that Ridolfi has letters of credit given him by the Spanish ambassador unto the duke of Alva; where upon he had a long conference with the duke and was dispatched to Rome with letters of credit to the King of Spain promising to be in Madrid the 20th of this month.

Touching the matter of secrecy committed unto him, I can learn nothing as yet, notwithstanding, I thought it my part to advertise tell your Lordship of this much which perhaps by other advertisements can give some guess what the same imports.

The Lord who reigns on high instituted a Church which should be one, and gave its government to Peter, and his successors. We labour with all our might to preserve that unity, now assailed by so many adversaries. Among them is that servant of infamy, Elizabeth, who styles herself Queen of England, the refuge of wicked men.

Having taken possession of the kingdom, she monstrously usurps the chief authority in the Church and fills the Royal Council with heretics.

We declare the said Elizabeth a heretic, and a fautor of heretics, and that all who adhere to her incur the sentence of anathema, and are cut off from the unity of the Body of Christ.

Moreover, that she has forfeited her pretended title to the aforesaid kingdom, and is deprived of all dominion, dignity, and privilege. We declare that nobles, subjects, and peoples are free from any oath to her, and we interdict obedience to her monitions, mandates, and laws.

From France, Walsingham picked up one thread of the mystery. In May 1571, he wrote Burghley that he had heard of Ridolfi's meeting with Alva and the fact that he was carrying with him letters of credence from the Spanish Ambassador in London; after a long conference with Alva, the Florentine had continued on to see both the Pope and the King of Spain. But what Ridolfi's secret business was, Walsingham had been completely unable to determine.

The break in the case came obliquely, explosively, in August. A merchant reported to Burghley a strange business that he thought his Lordship should know of. The merchant had been asked by the Duke of Norfolk to carry a shipment north. The load seemed unusually heavy; upon investigation, it turned out to be £600 in gold, plus several letters in cipher.

Burghley quickly arrested the Duke's secretary and ordered a search of the Duke's great London house. He was hoping to find the cipher key, but his searchers instead found.yet another cipher letter, hidden, with a subtlety well befitting the Duke's skills as a conspirator, under a mat at the entrance to his bedroom.

The Duke's sweating secretary at this point, under further interrogation, suddenly remembered that the Duke had received letters in cipher from the Queen of Scots; it was a point that had slipped his mind until then.

The Bishop of Ross, who had passed a not unpleasant summer in the custody of the Bishop of Ely at his country house, hunting and amiably debating theology, was now brought to the Tower and threatened with more rigorous interrogation himself. He pleaded diplomatic immunity; Burghley countered with a written opinion from the Doctors of Law that "an ambassador procuring an insurrection or rebellion in the Prince's country toward whom he is an ambassador" has forfeited this privilege; whereupon Ross spilled his guts.

Norfolk, he confessed, had been in on the plot from the start. The Duke was in fact the mysterious "40" to whom Ridolfi's progress report had been addressed; "30" was Lord Lumley, a leading Catholic nobleman. Ridolfi had carried letters and money from the Pope to advance the effort. Norfolk had refused to put his name directly to the letters Ridolfi had carried abroad from de Spes, letters that Ross now admitted laid out the whole invasion plan to Alva and the Pope; but Ross and Ridolfi had personally assured de Spes that Norfolk had given his word that he subscribed to the plan, and on that basis the Spanish Ambassador had agreed to lend his support. The plan that Norfolk had endorsed envisioned the Catholic lords assembling 20,000 infantry and 3,000 horse; Alva would supply 6,000 arquebusiers, 3,000 horse, and 25 pieces of field artillery. Harwich was the port most suitable for the invasion force. The plan also called for two diversionary forces, z,ooo men each, to be sent to Scotland and Ireland. Included in Ridolfi's letters were a list of 40 English noblemen likely to stand with the rebellion.

Ross was so terrified of the rack that once he began confessing he could scarcely stop. He dashed off a letter to Mary commending her henceforth to trust only to God; it was obviously His providence that so misguided a plot as this had been uncovered. In a rush of anguish, Ross blurted out to his interrogator, Dr. Thomas Wilson, that Mary had practically murdered all three of her husbands, was unfit to be any man's wife.

"Lord, what a people are these!" Thomas remarked to Burghley afterward. "What a Queen, and what an ambassador."

The plot was ludicrous in many ways; it would much later be known that, although Alva approved of its purpose, he thought Ridolfi a fool and that an invasion made sense only if Elizabeth was first killed or deposed. "A man like this," Alva wrote to Philip of Ridolfi, "who is no soldier, who has never witnessed a campaign in his life, thinks that armies can be poured out of the air, or kept up one's sleeve, and he will do with them whatever fancy suggests."

Realistic or not, it was indubitably treasonous. Norfolk was rearrested and, "falling on his knees, confessed his undutiful and foolish doings," reported the gentlemen who had been sent to bring him to the Tower. The Duke was carried through the streets of London "without any trouble," his escorts added, "save a number of idle, rascal people, women, men, boys, girls, running about him, as the manner is, gaffing at him."

The realm's last duke was arraigned and condemned by a jury of his peers, and sent to the scaffold on the and of June 1572. The Spanish Ambassador was expelled; in a parting shot, he tried to encourage two glory-dreaming English Catholics to assassinate Burghley, a plot that promptly unraveled when the men sent an anonymous letter to Burghley warning him of it themselves.

Ridolfi dispatched one final letter to Mary from Paris, lamenting that circumstances, alas, did not permit him to return to England. Made a Senator of Rome by the Pope, he peacefully lived out the remainder of his eighty years, dying in his native Florence in 1612.

Ross, and Baillie, were eventually released: All things come to those who wait.

Mary was ordered to reduce the size of her entourage to sixteen servants. She wrote more pathetic pleas to Elizabeth and Burghley bemoaning her "feeble state" and that of her faithful, dismissed servants.

Roberto Ridolfi, a Florentine banker, whose optimism was based on a hopeless inability to understand the temper of the English nation, had evolved a plan to seize the Queen and Council, liberate Mary Stuart and place her on the English throne and restore the Catholic religion. Through the Bishop of Ross he brought Norfolk into touch with Mary once more, and Mary, far distant as she was, rekindled in his mind the fatal enthusiasm for her cause.

In the four major plots in which she was concerned during her eighteen years' imprisonment, the crucial question in each case was whether she had plotted or connived at the murder of Elizabeth. Her own story was that she never had. She had, naturally, and as she always said she would, used every means to gain her own freedom, but her plans, she swore most solemnly, had never included the murder of the English Queen. She had sworn, too, that she never intended the murder of her husband, who was now festering in his shroud.

Ridolfi had received through Ross a paper of detailed instructions agreed on by Mary and Norfolk; these empowered him to ask the Duke of Alva for guns, ammunition, armour and money, and 10,000 men, of whom 4,000, it was suggested, might make a diversion in Ireland. The instructions contained a clause that the most important part of Ridolfi's mission he would convey by word of mouth only.

Ridolfi went to Brussels, where the much-tried Alva heard him with mounting annoyance and dismay. Alva was holding his position in the Netherlands only with difficulty, and the suggestion that he should send away 10,000 of his men took no account of what was to happen behind their backs. Ridolfi went on his way towards Madrid and Alva sent express to the Spanish Ambassador at the Papal Court, urging him to give the Pope a realistic account of the difficulties inherent in the scheme; otherwise, he feared that the Pope's would be yet another voice, assuring him at a great distance from the scene of action that with the forces at his command, the conquest of England might readily be undertaken. He then wrote to Philip: he said that to wage a serious war in England would be out of the question, and this was what invasion would mean-so long as Elizabeth were alive. "But," he wrote, "if the Queen of England should die, either a natural or any other death" - then he would feel justified in lending troops for a rapid operation to put Mary Stuart on the vacant throne.

Ridolfi arrived in Madrid and presented his written credentials. As he then stated that Elizabeth was to be murdered, it is assumed that this was the subject of the instructions that were too compromising to write down. Later in the day, the Council of State debated his mission. The invasion of England and the assassination of its Queen were discussed as two parts of the same operation.

The most tepid member of the Council was the King himself. His heavy commitments against the Moors in the south east of Spain, the Turks in the Mediterranean and the revolting Netherland provinces, as well as his natural dislike of rash enterprises, made Philip fully agree with Alva that nothing expensive should be done for the plotters until they had done something for themselves. Let them seize the Council and put the Queen to death; then they should have help to maintain their position.

Ridolfi had failed to get help abroad; he now plunged the conspirators in ruin at home. He wrote full and compromising reports of his interviews with Alva to the Queen of Scots, Norfolk, the Bishop of Ross and de Spes, and sent them in cipher to England by his agent Bailly. Burleigh's watch on the ports was so close that Bailly was arrested at Dover. He was taken to the Tower and tortured on the rack, and the information wrung from him led to the arrest of the Bishop of Ross.