The Lost Letters of an Imprisoned Queen Have Been Decrypted After 400 Years

Mary, Queen of Scots' letters were decoded by a team of codebreakers in a discovery described as a "a literary and historical sensation."
Mary Queen of Scots
Mary Queen of Scots. Image: mikroman6 via Getty Images
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Deep in the digital archives of France’s national library, a collection of letters scratched out in unusual symbols were sitting neglected in a mislabeled folder until a trio of unlikely codebreakers—a computer scientist, a musician, and a physicist—revealed their historic origin, a feat that’s being publicized in a new study.

Using a code breaking algorithm and manual analysis, the team led by computer scientist George Lasry were able to decode the forgotten letters and identify them as the lost writings from Mary Queen of Scots (or, Mary Stuart) in the years leading up to her beheading in 1587. 


In the 57 letters that Lasry and colleagues decoded as part of the DECRYPT project, 50,000 previously unknown words were added to the historical canon. The findings were published Tuesday in the journal Cryptologia

The writings reveal new insight on subjects like Stuart’s imprisonment by her cousin Queen Elizabeth I, negotiations for her release, and distress over her son James’ (later, King James I of England) abduction. 

While humans have been breaking codes as long as they’ve been in use, Lasry told Motherboard in an email that the use of a computer algorithm to start the ball rolling is a huge asset.

“Historically, such codes were solved manually, with a lot of try-and-error…[but] this could take from days or weeks up to months to never,” Lasry said. “The computerized process is in a sense similar to the manual one, except that we are doing it mechanically, less relying on human intuition.” 

While the code used in Stuart’s letters was relatively complex, the authors wrote in the study that it still followed a typical pattern of the time which included using homophones (non-word symbols used to represent letters in the alphabet) and a nomenclature (symbols representing commonly used names or words.) 

In the paper, the authors wrote that these symbols could include “geometrical shapes, Latin or Greek letters, alchemy and astronomy symbols, letter variants, and Arabic figures.”


To begin deciphering these letters, the team’s algorithm began by approximating the deciphering of Stuart’s letters to solving a problem of optimization. In other words, solving how to get increasingly close to a readable solution by producing and then refining random keys. In particular, the algorithm was working to crack the code on the homophones used in the cipher and left decoding the nomenclature to human hands. 

Using this method, the team was astonished to discover the identity of the writer, which they further confirmed by comparing it to samples of already deciphered letters from Stuart. 

“This discovery is a literary and historical sensation,” said preeminent Mary Stuart historian, John Guy, in a statement. “This is the most important new find on Mary Queen of Scots for 100 years.”

Coincidentally, it was previously deciphered letters from Stuart on the topic of her cousin, including an alleged assassination plan, that would eventually lead to Stuart’s beheading in 1587.

Now that these lost letters have been brought to light, Lasry and colleagues hope that efforts to further understand and contextualize them can be undertaken. With already 50,000 new words ready for analysis, the team hope to collaborate with historians on these deciphered letters to include them in an annotated book to better understand Stuart’s years in captivity.