Mary, Queen of Scots’ Secret Letters Found and Decrypted

One of the ciphered letters, F38, identified by Lasry and his team.
George Lasry, Norbert Biermann and Satoshi Tomokiyo

In 1587, after enduring 19 years of imprisonment for allegedly helping hatch a plan to murder her cousin Queen Elizabeth I, Mary, Queen of Scots was beheaded. She was only 44. However, despite living a life of fear and solitude, it would appear that Mary made sure she wasn’t silenced. 

On Wednesday, marking the anniversary of Mary’s execution, an eclectic team of experts announced in the UK that they uncovered more than 55 encrypted letters written by the notorious royal during her time in captivity — 50 of which have never been seen before. 

Serendipitously, the trio — a cryptographer, a pianist and a physicist — stumbled upon this treasure box of letters while perusing the national library of France’s online archives for interesting enciphered documents. 

The nearly five dozen pieces were listed as from the first half of the 16th century and related to Italian matters, but upon further analysis, it was undeniable that they “had nothing to do with Italy,” the team said. 

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Some of the decoded words and phrases uncovered by the team.

George Lasry, Norbert Biermann and Satoshi Tomokiyo

Rather, they were written in French and belonged to Mary. 

Words relating to “captivity” kept popping up for instance, as did references to the name “Walsingham,” which was also the name of Elizabeth I’s spymaster. Lo and behold, Mary had sealed her deepest, darkest thoughts in a unique, private cipher system. And after extensively studying the secret correspondence Mary constructed with symbols, signals and puzzling line drawings, the crew finally cracked her code. 

“It kind of felt surreal,” George Lasry, lead author of a study on the find, computer scientist and cryptographer, said in a statement. “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.”

Brilliant in itself, this is also a huge deal because while historians had a strong inkling that these letters existed, actual proof of such documents had long been considered lost to time.

“Mary, Queen of Scots has left an extensive corpus of letters held in various archives,” Lasry said. “There was prior evidence, however, that other letters from Mary Stuart were missing from those collections, such as those referenced in other sources but not found elsewhere.”

Bingo. The team’s fresh-off-the-press decryptions, dated between 1578 and 1584, are most likely snippets of that secret correspondence. 

A restored portrait of Mary, Queen of Scots.

Getty Images

Oh, Castelnau!

An incredible walkthrough of how the team decoded the letters and an outline of the subtleties they found can be seen in a paper published about the ordeal in the journal Cryptologia. But to sum it up, there were a few major topics revealed by the team’s codebreaking. 

First off, and perhaps most notably, Mary spoke at great length about her poor health due to the conditions of prisons she lived in. She also often asks about how negotiations are going with Queen Elizabeth I regarding her release from confinement. Although Mary was convicted in 1567 for plotting Elizabeth I’s murder, she pretty much maintained her innocence — but even today, historians still aren’t sure of the truth. 

That’s probably because Mary’s entire life was like a cryptogram itself, riddled with conspiracies, covert operations and mystery.

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A copy of a code between Mary and Castelnau, previously found in Castelnau’s notes.

George Lasry, Norbert Biermann and Satoshi Tomokiyo

Mary was charged for her supposed crimes through muddled terms to begin with. The timeline traces back to when her second husband Henry Stuart or Lord Darnley (who she allegedly didn’t really care for) was found strangled. His body had been located in a house he was staying in… that was also bombed with barrels full of gunpowder hidden beneath his bedroom.

Naturally, lots of people thought Darnley’s death was murder. And they pointed their fingers at Mary. 

Then, Mary tried to get Elizabeth I’s support in light of these accusations, which her cousin initially sort of offered, but eventually Elizabeth I had her imprisoned for the deed. However, as some historians contend, Elizabeth I likely imprisoned Mary not for valid reasons but because she was worried Mary wanted to overthrow her claim to the throne. 

Then, a bunch of strange documents, including letters, marriage contracts and literally sonnets, showed up in a silver casket belonging to Mary after she fled Scotland. They seemingly offered solid evidence that Mary wanted to kill Darnley. But what’s weird about the casket letters is many of the documents were produced for the court by Mary’s half-brother — and political enemy. Plus, they weren’t signed or dated. 

Yet, they looked to be in Mary’s handwriting. Confusing. 

Returning to the team’s newly deciphered letters, fascinatingly, some touch on a bunch of big moments in this saga.

A few, for instance, emphasize Mary’s mistrust of Elizabeth I’s spymaster Sir Francis Walsingham as well as one of Elizabeth I’s close friends, Robert Dudley, Earl of Leicester. 

More specifically, Mary describes Walsingham as “cunning,” falsely offering friendship while concealing his true intentions, the study authors write. She also steadfastly warns that some people working for her might be Walsingham’s secret agents. This latter bit, according to the study’s authors, turned out to be correct.

And if you’re wondering who exactly Mary is telling her secrets to in such securely encrypted memos, the answer is (mostly) Michel de Castelnau de Mauvissière, the French ambassador to England. Among 57 letters analyzed as part of the recent codebreaking, the authors write, 54 were addressed to Castelnau. 

Needless to say, he was also a strong supporter of the captive queen. 

This previously discovered cipher that decoded message between Mary and Châteauneuf, the French ambassador in London after Castelnau, has some similarities with the newly decrypted cipher between Mary and Castelnau.

George Lasry, Norbert Biermann and Satoshi Tomokiyo

For example, a major recurrent topic, per the study, has to do with Mary’s efforts to maintain a secure communication channel with Castelnau. This confidential channel, they say, operated in parallel with an official channel under Walsingham’s supervision through which, “in Mary’s own words, she would never write anything that she did not want even her worst enemies to be able to read.”

And in one letter from 1583, Mary writes:

“Monsieur de Mauvissiere, you have given me great pleasure in informing me amply, as you have done in your last two letters, of your proceedings on this new offer and negotiations for my freedom … I have written to the queen of England as you have advised me, and by word of mouth I have instructed Beale, as he sees fit, to convey to Burghley, Leicester and Walsingham and others of the Council the sincerity of my intention toward their said queen, themselves, and this state.”

A special graphical user interface that the team used to decrypt the found letters.

George Lasry, Norbert Biermann and Satoshi Tomokiyo

“This is the most important new find on Mary Queen of Scots for 100 years,” Jon Guy, who wrote a 2004 biography of Mary Queen of Scots, said in a statement. “I’d always wondered if de Castelnau’s originals could turn up one day, buried in the Bibliotheque Nationale de France or perhaps somewhere else, unidentified because of the ciphering. And now they have.”

And in Guy’s opinion, those weird casket letters? He once wrote that they were merely “a fix by Mary’s enemies to destroy her, an ingenious, devious one.”