The Code Book: The Secret History of Codes and Code-breaking. Simon Singh

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      Figure 9 The forged postscript added by Thomas Phelippes to Mary’s message. It can be deciphered by referring to Mary’s nomenclator (Figure 8).

       Public Record Office, London.

      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.

      Soon after receiving the message and its postscript, Babington needed to go abroad to organise the invasion, and had to register at Walsingham’s department in order to acquire a passport. This would have been an ideal time to capture the traitor, but the bureaucrat who was manning the office, John Scudamore, was not expecting the most wanted traitor in England to turn up at his door. Scudamore, with no support to hand, took the unsuspecting Babington to a nearby tavern, stalling for time while his assistant organised a group of soldiers. A short while later a note arrived at the tavern, informing Scudamore that it was time for the arrest. Babington, however, caught sight of it. He casually said that he would pay for the beer and meal and rose to his feet, leaving his sword and coat at the table, implying that he would return in an instant. Instead, he slipped out of the back door and escaped, first to St John’s Wood and then on to Harrow. He attempted to disguise himself, cutting his hair short and staining his skin with walnut juice to mask his aristocratic background. He managed to elude capture for ten days, but by 15 August Babington and his six colleagues were captured and brought to London. Church bells across the city rang out in triumph. Their executions were horrid in the extreme. In the words of the Elizabethan historian William Camden, ‘they were all cut down, their privities were cut off, bowelled alive and seeing, and quartered’.

      Meanwhile, on 11 August, Mary Queen of Scots and her entourage had been allowed the exceptional privilege of riding in the grounds of Chartley Hall. As Mary crossed the moors she spied some horsemen approaching, and immediately thought that these must be Babington’s men coming to rescue her. It soon became clear that these men had come to arrest her, not release her. Mary had been implicated in the Babington Plot, and was charged under the Act of Association, an Act of Parliament passed in 1584 specifically designed to convict anybody involved in a conspiracy against Elizabeth.

      The trial was held in Fotheringhay Castle, a bleak, miserable place in the middle of the featureless fens of East Anglia. It began on Wednesday 15 October, in front of two chief justices, four other judges, the Lord Chancellor, the Lord Treasurer, Walsingham, and various earls, knights and barons. At the back of the courtroom there was space for spectators, such as local villagers and the servants of the commissioners, all eager to see the humiliated Scottish queen beg forgiveness and plead for her life. However, Mary remained dignified and composed throughout the trial. Mary’s main defence was to deny any connection with Babington. ‘Can I be responsible for the criminal projects of a few desperate men’, she proclaimed, ‘which they planned without my knowledge or participation?’ Her statement had little impact in the face of the evidence against her.

      Mary and Babington had relied on a cipher to keep their plans secret, but they lived during a period when cryptography was being weakened by advances in cryptanalysis. Although their cipher would have been sufficient protection against the prying eyes of an amateur, it stood no chance against an expert in frequency analysis. In the spectators’ gallery sat Phelippes, quietly watching the presentation of the evidence that he had conjured from the enciphered letters.

      The trial went into a second day, and Mary continued to deny any knowledge of the Babington Plot. When the trial finished, she left the judges to decide her fate, pardoning them in advance for the inevitable decision. Ten days later, the Star Chamber met in Westminster and concluded that Mary had been guilty of ‘compassing and imagining since June 1st matters tending to the death and destruction of the Queen of England’. They recommended the death penalty, and Elizabeth signed the death warrant.

      On 8 February 1587, in the Great Hall of Fotheringhay Castle, an audience of three hundred gathered to watch the beheading. Walsingham was determined to minimise Mary’s influence as a martyr, and he ordered that the block, Mary’s clothing, and everything else relating to the execution be burned in order to avoid the creation of any holy relics. He also planned a lavish funeral procession for his son-in-law, Sir Philip Sidney, to take place the following week. Sidney, a popular and heroic figure, had died fighting Catholics in the Netherlands, and Walsingham believed that a magnificent parade in his honour would dampen sympathy for Mary. However, Mary was equally determined that her final appearance should be a defiant gesture, an opportunity to reaffirm her Catholic faith and inspire her followers.

      While the Dean of Peterborough led the prayers, Mary spoke aloud her own prayers for the salvation of the English Catholic Church, for her son and for Elizabeth. With her family motto, ‘In my end is my beginning’, in her mind, she composed herself and approached the block. The executioners requested her forgiveness, and she replied, ‘I forgive you with all my heart, for now I hope you shall make an end of all my troubles’. Richard Wingfield, in his Narration of the Last Days of the Queen of Scots, describes her final moments:

      Then she laide herself upon the blocke most quietlie, & stretching out her armes & legges cryed out In manus tuas domine three or foure times, & at the laste while one of the executioners held her slightlie with one of his handes, the other gave two strokes with an axe before he cutt of her head, & yet lefte a little gristle behinde at which time she made verie small noyse & stirred not any parte of herself from the place where she laye … Her lipps stirred up & downe almost a quarter of an hower after her head was cutt of. Then one of her executioners plucking of her garters espied her little dogge which was crept under her clothes which could not be gotten forth but with force & afterwardes could not depart from her dead corpse, but came and laye betweene her head & shoulders a thing dilligently noted.