Catholic plots and Walsingham's spies, 1571–87
After the Northern Earls failed in open battle, Catholic resistance went underground. Between 1571 and 1586 three serious conspiracies aimed to assassinate Elizabeth, free Mary, Queen of Scots, and put her on the English throne with Spanish or French troops behind her. Each one was caught. The reason they were caught matters as much as the plots themselves: Sir Francis Walsingham, Elizabeth’s Principal Secretary, had built the most sophisticated intelligence network in Europe.
The three major plots all centred on Mary, Queen of Scots: the Ridolfi Plot (1571) was a Spanish-backed plan to depose Elizabeth and crown Mary; the Throckmorton Plot (1583) was a French- and Spanish-backed invasion plan; the Babington Plot (1586) aimed to assassinate Elizabeth and was the trap that finally caught Mary.
The Ridolfi Plot, 1571
Roberto Ridolfi was a Florentine banker living in London with contacts in Madrid and Rome. His 1571 plan was to coordinate a Spanish invasion from the Netherlands under the Duke of Alva, an English Catholic rising led by the Duke of Norfolk, and the assassination of Elizabeth — all to put Mary on the throne and marry her to Norfolk.
Walsingham, then ambassador to France, intercepted coded correspondence and worked with Cecil to crack the cipher. Ridolfi himself was abroad when his courier was arrested at Dover with incriminating papers. Norfolk — already pardoned once for his role in 1569 — was arrested, tried for treason and executed in June 1572. Mary remained alive in custody, but Parliament now demanded harsher action against her.
The Throckmorton Plot, 1583
Francis Throckmorton was a young Catholic gentleman who acted as a courier between Mary and the Spanish ambassador in London, Bernardino de Mendoza. The 1583 plan was an invasion by French Catholic forces under the Duke of Guise, funded by Philip II of Spain, accompanied by an English Catholic rising. Walsingham’s agents had been watching Throckmorton for six months.
When his house was searched, agents found a list of English Catholic supporters and details of suitable invasion ports. Under torture, Throckmorton confessed; he was executed in July 1584. Mendoza was expelled from England — the last Spanish ambassador permitted on English soil. Parliament passed the 1585 Act for the Queen’s Surety, declaring that anyone in whose name a plot was made could be tried and executed. Mary was now legally exposed.
It is easy to picture Mary as the mastermind because every plot was named ‘for Mary’. In reality she was a closely watched prisoner moved between Tutbury, Sheffield, Chartley and Fotheringhay. Ridolfi was the Florentine banker’s scheme; Throckmorton was a courier passing letters; only the Babington Plot produced a letter in Mary’s own hand explicitly approving Elizabeth’s assassination — and even that exists because Walsingham deliberately allowed the correspondence to flow so that she would commit herself in writing. Top-band answers separate Mary’s claim (the magnet) from her active leadership (much smaller than the legend).
Walsingham’s Intelligence Network
By the early 1580s Sir Francis Walsingham — Principal Secretary from 1573 — ran an intelligence service of around 50 agents across England and Europe, paid for partly out of his own pocket. His chief cryptanalyst, Thomas Phelippes, could break almost any contemporary cipher. Agents intercepted letters, opened them, copied them, recoded them and sent them on so the recipients suspected nothing. Catholic priests entering England were tracked from the moment they landed. Imprisoned suspects were interrogated, often under torture authorised by the Privy Council.
For the Mary problem specifically, Walsingham organised what would now be called a sting. He arranged for Mary to be moved to Chartley Hall in 1585 and let her believe she had a secret channel for letters — smuggled in beer barrels by a brewer. Every letter was already being read. The trap was set; he simply needed someone reckless enough to step into it.
The Babington Plot, 1586
Anthony Babington was a wealthy Catholic gentleman in his mid-twenties. In July 1586 he wrote to Mary outlining a plan to assassinate Elizabeth, free Mary, and welcome a Spanish-backed invasion. Walsingham’s team intercepted the letter, read it, copied it — and waited.
Mary’s reply on 17 July 1586 explicitly approved the assassination of Elizabeth. Phelippes added a forged postscript asking Babington to name his fellow conspirators, then resealed the letter and let it through. Babington named them. By August every plotter was in custody. Babington and six others were hanged, drawn and quartered in September 1586. Mary was tried at Fotheringhay Castle in October under the 1585 Act; her own letter sealed her fate.
Mary was tried at Fotheringhay in October 1586 and condemned to death. Elizabeth delayed signing the warrant for months. When she finally signed in February 1587, William Cecil and the Privy Council acted immediately — Mary was beheaded at Fotheringhay on 8 February 1587. Elizabeth publicly blamed her secretary, Davison, for sending the warrant.
Why Mary Was Executed in 1587
The execution had multiple causes. The Babington letter gave incontrovertible written proof, removing Elizabeth’s usual legal cover. The 1585 Act for the Queen’s Surety had been designed for exactly this. Parliament and the Privy Council, especially William Cecil and Walsingham, had been pushing for years. Spanish preparations for an invasion fleet were already visible — killing Mary removed Catholic Europe’s legitimate alternative monarch and put Spain in a corner. Elizabeth’s own famous prevarication — she signed, then claimed she had not meant the warrant to be used — reflected the political risk: executing an anointed queen was unprecedented and gave Philip II a Catholic martyr to exploit.
Connect the plots into a chain rather than describing each in turn. Ridolfi (1571) cost Norfolk his head and pushed Parliament to demand action against Mary. Throckmorton (1583) produced the 1585 Act for the Queen’s Surety. Babington (1586) gave the legal proof to use that Act against Mary herself. Each plot drove a tougher law that made the next plot easier to prosecute — and Mary’s execution in 1587 then removed Spain’s legitimate cover, leading directly to the Armada the following year.
The plots show two things. First, that the threat to Elizabeth was genuine and persistent — without Walsingham, Cecil, Phelippes and the network they ran, one of these schemes would probably have succeeded. Second, that Elizabeth was not making these decisions alone. Do not treat the Privy Council as a vague entity; the named figures — Cecil at Treasury, Walsingham at intelligence, Phelippes on ciphers — are the difference between a vague answer and a top-band one.