Decoders break Mary, Queen of Scots’ secret code in letters she sent while imprisoned

Secret letters written by Mary, Queen of Scots while she was imprisoned by Elizabeth I, have been decoded for the first time in nearly 450 years, in a major historical breakthrough.

Cryptographers stumbled upon the finds while hunting for enciphered documents in the online archives of the National Library of France (Bibliotheque nationale de France.)

Most of the 57 letters were written between Mary and the French ambassador to England, Michel de Castelnau de Mauvissière, and penned while she was under house arrest at the Earl of Shrewsbury’s home in Sheffield.

They date between 1578 and 1584, ending just a few years before she was beheaded on Feb 8, 1587.

The letters show Mary’s attempts to regain the Scottish throne and ensure the future of her son James, while attempting to negotiate her release and intervene in politics on the continent. She also speaks of plots against her and complains of the poor conditions of her imprisonment.

'Literary and historical sensation'

Historian Dr Jon Guy, a Mary, Queen of Scots expert from Cambridge University, said: “These discoveries will be a literary and historical sensation. They mark the most important new find on Mary Stuart, Queen of Scots, for 100 years.

“The letters show definitively that Mary, during the years of her captivity in England in the Earl of Shrewsbury’s custody, closely observed and actively involved herself in political affairs in Scotland, England and France, and was in regular contact, either directly, or indirectly through de Castelnau, with many of the leading political figures at Elizabeth I’s court.

“These new documents, amounting to some 50,000 words, show Mary to have been a shrewd and attentive analyst of international affairs. They will occupy historians of Britain and Europe and students of the French language and early modern ciphering techniques for many years to come.”

The letters were uncovered by George Lasry, an independent cipher expert and computer scientist; Norbert Biermann, a pianist and music professor from the Berlin University of Arts, and Satoshi Tomokiyo who runs the code breaking website Cryptania.

The documents - written in a fiendish cipher of 219 symbols - had been wrongly catalogued as “relating to Italian matters” but after feeding the text into a computer code breaking algorithm, the trio were amazed to spot a few words in French.

Those few words, which included “prochain” - next - “temps” - time - and “moins” - less - were able to give an indication of which symbols stood for certain letters, but the team quickly realised there was far more going on in the cipher.

For example, the discovery of a specific symbol had been used to signal that the previous letter should be repeated, while another was used when the previous letter should be deleted. A separate symbol indicated a full stop.

Different symbols had also been used for parts of words such as the “que” in catholiques (catholics) as well as the “ant” in advantage, and “ion” in “persecution”.

Frequently used words, such as king (roy), queen (royne), “monsieur” and “madame” all had their own symbols, while a capital “C” stood for the King of France, and a lower case “d” the King of Spain.

To make the code even more tricky there were interchangeable symbols for some vowels and consonants, as well as separate symbols for nouns such as names or months.

“Upon deciphering the letters, I was very, very puzzled and it kind of felt surreal,” said Mr Lasry, who is also part of the DECRYPT Project, which works with universities across Europe, to digitise, transcribe, and decode historical ciphers.

“We have broken secret codes from kings and queens previously, and they’re very interesting but with Mary, Queen of Scots it was remarkable as we had so many unpublished letters deciphered and because she is so famous.

“This is a truly exciting discovery. Together, the letters constitute a voluminous body of new primary material on Mary Stuart – about 50,000 words in total, shedding new light on some of her years of captivity in England.”

Mary, who was born in 1842, became Queen of Scotland at just six days old, but was sent to France when she was six and was brought up in the French court, eventually marrying the Dauphin Francis.

Although Francis became king, he died within a year of taking the throne and Mary moved back to Scotland. Following the death of her second husband, nobles turned against her and she was forced to flee to England where she was imprisoned by Elizabeth I who feared she would try to take the throne.

Descended from Henry VIII’s sister, Mary had a claim to the English throne, and many Catholics believed she was the legitimate queen, not recognising the marriage between Henry and Anne Boleyn, Elizabeth’s mother.

Viewed as too great a threat, she was imprisoned for 19 years, and eventually put to death aged 44 in 1587 for her part in an alleged plot to kill Elizabeth.

The new research was published in a special issue of the journal Cryptologia.