Mary Stuart, Queen of Scotland and dowager Queen of France, returned to Scotland in 1561 a foreigner in the land she ruled. She married again and gave birth to a son, the future James VI, before being implicated in her husband's murder and deposed.

It only got worse after that. She escaped her imprisonment a year later and fled to England seeking help from Queen Elizabeth, but since Mary was the daughter of Henry VIII's sister, she had a claim to the throne of England also. And since Henry VIII had created a competitor to the Catholic church in order to run off with all the women he wanted (he was the head of the Anglican church and could annul anything he liked) Elizabeth was disliked by Catholics.

Like many royals engaged in geopolitics, she was involved in a lot of plots, or at least named, but her final one, the assassination of Queen Elizabeth, got her beheaded. 


Sample ciphertext – F38 (Source: gallica.bnf.fr/BnF fr. 2988 f.38).

Like many royals, she wrote in code, most often a substitution cypher, but many of her letters seemed to be missing. A few dozen have now been discovered in France, previously unknown because they were both in code and had no date, writer, or recipient, New sleuthing by The DECRYPT Project reveals nearly all were written to Michel de Castelnau, French Ambassador to England. 


Figure 13. Mary-Castelnau cipher – 1.

It is what you expect from a monarch in need to a politician competing against her captor; she stays vague, assuming the letters might be intercepted, and even offers aid to Elizabeth, while telling the French ambassador not to mention that the knowledge came from Mary. She worries about her son, while attempting to remove him from the throne and "co-rule" instead.

Her plots, both real and the ones invoking her, proved her undoing but her son was wiser in avoiding her machinations. James VI of Scotland did becpme James I of England and unified the thrones, something Scotland would later fight (and fail) to undo. James is King Charles' 10th-great-grandfather and I am descended on my mother's side. But our family left for America after the line of Stuarts had declined and Scottish nobles went into bankruptcy, ruining most of the country - they had founded a colony, New Caledonia, in Panama, with disastrous consequences - allowing England to change it from a personal union to a formal one in 1707.