On the 12th of July, 1571, Philip wrote to the Duke of Alva, giving an account of his interview with Roberto Ridolfi.  The envoy, after relating the sufferings of the Queen of Scotland, had laid before him a plan for her liberation.  If the Spanish monarch were willing to assist the Duke of Norfolk and his friends, it would be easy to put upon Mary’s head the crown of England.  She was then to intermarry with Norfolk.  The kingdom of England was again to acknowledge the authority of Rome, and the Catholic religion to be everywhere restored.  The most favorable moment for the execution of the plan would be in August or September.  As Queen Elizabeth would at that season quit London for the country, an opportunity would be easily found for seizing and murdering her.  Pius V., to whom Ridolfi had opened the whole matter, highly approved the scheme, and warmly urged Philip’s cooperation.  Poor and ruined as he was himself; the Pope protested that he was ready to sell his chalices, and even his own vestments, to provide funds for the cause.  Philip had replied that few words were necessary to persuade him.  His desire to see the enterprize succeed was extreme, notwithstanding the difficulties by which it was surrounded.  He would reflect earnestly upon the subject, in the hope that God, whose cause it was, would enlighten and assist him.  Thus much he had stated to Ridolfi, but he had informed his council afterwards that he was determined to carry out the scheme by certain means of which the Duke would soon be informed.  The end proposed was to kill or to capture Elizabeth, to set at liberty the Queen of Scotland, and to put upon her head the crown of England.  In this enterprize he instructed the Duke of Alva secretly to assist, without however resorting to open hostilities in his own name or in that of his sovereign.  He desired to be informed how many Spaniards the Duke could put at the disposition of the conspirators.  They had asked for six thousand arquebusiers for England, two thousand for Scotland, two thousand for Ireland.  Besides these troops, the Viceroy was directed to provide immediately four thousand arquebuses and two thousand corslets.  For the expenses of the enterprize Philip would immediately remit two hundred thousand crowns.  Alva was instructed to keep the affair a profound secret from his councillors.  Even Hopper at Madrid knew nothing of the matter, while the King had only expressed himself in general terms to the nuncio and to Ridolfi, then already on his way to the Netherlands.  The King concluded his letter by saying, that from what he had now written with his own hand, the Duke could infer how much he had this affair at heart.  It was unnecessary for him to say more, persuaded as he was that the Duke would take as profound an interest in it as himself.