In March 1586, Anthony Babington and six friends gathered in The Plough, an inn outside Temple Bar, where they discussed the possibility of freeing Mary, assassinating Elizabeth, and inciting a rebellion supported by an invasion from abroad. With his spy network, it was not long before Walsingham discovered the existence of the Babington Plot. To make sure he obtained a conviction he arranged for Gifford to visit Babington on 6th July. Gifford told Babington that he had heard about the plot from Thomas Morgan in France and was willing to arrange for him to send messages to Mary via his brewer friend. (1)
However, Babington did not fully trust Gifford and enciphered his letter. Babington used a very complex cipher that consisted of 23 symbols that were to be substituted for the letters of the alphabet (excluding j. v and w), along with 35 symbols representing words or phrases. In addition, there were four nulls and a sybol which signified that the next symbol represents a double letter. It would seem that the French Embassy had already arranged for Mary to receive a copy of the necessary codebook. (2)
Gilbert Gifford took the sealed letter to Francis Walsingham. He employed counterfeiters, who would then break the seal on the letter, make a copy, and then reseal the original letter with an identical stamp before handing it back to Gifford. The apparently untouched letter could then be delivered to Mary or her correspondents, who remained oblivious to what was going on. (3)
The copy was then taken to Thomas Phelippes. Cryptanalysts like Phelippes used several methods to break a code like the one used by Babington. For example, the commonest letter in English is "e". He established the frequency of each character, and tentatively proposed values for those that appeared most often. Eventually he was able to break the code used by Babington. The message clearly proposed the assassination of Elizabeth.
Francis Walsingham now had the information needed to arrest Babington. However, his main target was Mary Queen of Scots and he therefore allowed the conspiracy to continue. On 17th July she replied to Babington. The message was passed to Phelippes. As he had already broken the code he had little difficulty in translating the message that gave her approval to the assassination of Elizabeth. Mary Queen of Scots wrote: "When all is ready, the six gentlemen must be set to work, and you will provide that on their design being accomplished, I may be myself rescued from this place." (4)
Walsingham had enough evidence to arrest Mary and Babington. However, to destroy the conspiracy completely, he needed the names of all those involved. He ordered Phelippes to forge a postscript to Mary's letter, which would entice Babington to name the other men involved in the plot. "I would be glad to know the names and qualities of the six gentleman which are to accomplish the designment; for it may be that I shall be able, upon knowledge of the parties, to give you some further advice necessary to be followed therein, as also from time to time particularly how you proceed."
Simon Singh, the author of The Code Book: The Secret History of Codes & Code-Breaking (2000) has pointed out: "The cipher of Mary Queen of Scots clearly demonstrates that a weak encryption can be worse than no encryption at all. Both Mary and Babington wrote explicitly about their intentions because they believed that their communications were secure, whereas if they had been communicating openly they would have referred to their plan in a more discreet manner. Furthermore, their faith in their cipher made them particularly vulnerable to accepting Phelippes's forgery. Sender and receiver often have such confidence in the strength of their cipher that they consider it impossible for the enemy to mimic the cipher and insert forged text. The correct use of a strong cipher is a clear boon to sender and receiver, but the misuse of a weak cipher can generate a very false sense of security." (5)
Walsingham allowed the letters to continue to be sent because he wanted to discover who else was involved in this plot to overthrow Elizabeth. Eventually, on 25th June 1586, Mary wrote a letter to Anthony Babington. In his reply, Babington told Mary that he and a group of six friends were planning to murder Elizabeth. Babington discovered that Walsingham was aware of the plot and went into hiding. He hid with some companions in St John's Wood, but was eventually caught at the house of the Jerome Bellamy family in Harrow. (6) On hearing the news of his arrest the government of the city put on a show of public loyalty, witnessing "her public joy by ringing of bells, making of bonfires, and singing of psalms". (7)
Babington home was searched for documents that would provide evidence against him. When interviewed, Babington, who was not tortured, made a confession in which he admitted that Mary had written a letter supporting the plot. At his trial, Babington and his twelve confederates were found guilty and sentenced to hanging and quartering. "The horrors of semi-strangulation and of being split open alive for the heart and intestines to be wrenched out were regarded, like those of being burned to death, as awful but in the accepted order of things." (8)
Gallows were set up near St Giles-in-the-Field and the first seven conspirators, led by Babington, were executed on 20th September 1586. Babington's last words were “Spare me Lord Jesus”. Another conspirator, Chidiock Tichborne, made a long speech where he blamed Babington "for drawing him in". (9) The men "were hanged only for a short time, cut down while they were still alive, and then castrated and disembowelled".
The other seven were brought to the scaffold the next day and suffered the same death, "but, more favourably, by the Queens commandment, who detested the former cruelty" They hung until they were dead and only then suffered the barbarity of castration and disembowelling. The last to suffer was Jerome Bellamy, who was found guilty of hiding Babington and the others at his family's house in Harrow. His brother cheated the hangman by killing himself in prison. (10)
We... will undertake the delivery of your royal persons from the hands of your enemies... For the dispatch of the usurper (Elizabeth)... six noble gentlemen, who, for the zeal they have to the Catholic cause... will undertake that tragical execution.
When all is ready, the six gentlemen must be set to work, and.... when it is accomplished, I may be in some way got away from here... then we will await foreign assistance.
There is a letter from the Scottish Queen, that hath wrought tears... the delay (in executing Mary) is too dangerous.
While Mary was in England, plot after plot was made against Elizabeth by Mary's friends, and by men who looked to her as their rightful queen. Whether Mary knew of these plots is uncertain... Letters were found... but there were many who said then, and many who still believe, that these letters were forgeries - that is to say, that they were written by Mary's enemies for the purpose of making people believe she was guilty.
The executioners, kneeling, desired her Grace to forgive them her death: who answered, "I forgive you with all my heart, for now, I hope, you shall make an end to all my troubles."... Then she, lying very still upon the block, one of the executioners holding her slightly with one of his hands, she endured two strokes of the axe... Her lips stirred up and down a quarter of an hour after her head was cut off.