Secret letters written by Mary Queen of Scots while she was imprisoned in England by her cousin Queen Elizabeth I have been decoded.
Experts said the codebreakers’ work is the most significant discovery about Mary for 100 years.
For centuries, the contents of the letters were believed to be lost.
That was until George Lasry, a computer scientist and cryptographer, Norbert Biermann, a pianist and music professor, and Satoshi Tomokiyo, who is a physicist and patents expert, stumbled upon them in the national library of France – Bibliotheque nationale de France (BnF).
The trio discovered that Mary had penned the letters after solving her cipher system.
Their work on 57 letters revealed 50 new scripts that historians were not aware of.
The letters date from 1578 to 1584, a few years before Mary’s beheading 436 years ago today – February 8 1587.
According to the decoders, the letters reveal fascinating insights on her captivity.
Most are addressed to Michel de Castelnau de Mauvissiere, the French ambassador to England, who was a supporter of Catholic Mary.
Mr Lasry, lead author of the study, said: “Upon deciphering the letters, I was very, very puzzled and it kind of felt surreal.
“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and queens previously, and they’re very interesting, but with Mary Queen of Scots it was remarkable as we had so many unpublished letters deciphered and because she is so famous.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.”
Part of the multi-disciplinary Decrypt Project involving several universities in Europe, with the goal of mapping, digitising, transcribing and deciphering historical ciphers, he added: “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, Queen of Scots, has left an extensive corpus of letters held in various archives.
“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.
“The letters we have deciphered… are most likely part of this lost secret correspondence.”
While in captivity, Mary communicated with her associates and allies, making extensive efforts to recruit messengers and to maintain secrecy.
The existence of a confidential communication channel between Mary and Castelnau is well-known to historians, and even to the English government at the time.
But the codebreakers provide new evidence that this exchange was in place as early as May 1578 and active until at least mid-1584.
Computer and manual techniques were used to decode the letters which show the challenges Mary faced maintaining links with the outside world, how the letters were carried and by whom.
Key themes in the correspondence include complaints about her poor health and conditions in captivity, and her negotiations with Queen Elizabeth I for her release, which she believed were not conducted in good faith.
The letters reveal her distrust of the queen’s spymaster, Sir Francis Walsingham, as well as her animosity towards Robert Dudley, Earl of Leicester and a favourite of Elizabeth.
She also expresses her distress when her son James (future King James I of England) is abducted in August 1582, and her feeling they have been abandoned by France.
Writing in this Special Issue version of Cryptologia, the authors describe how some of the letters were in a large set of unmarked documents in cipher and using the same set of graphical symbols.
The BnF catalogue listed them as from the first half of the 16th century, and related to Italian matters.
However, the study authors say that soon after starting to crack the code, they quickly realised they were written in French and were nothing to do with Italy.
Their work revealed verbs and adverbs often in the feminine form, several mentions of captivity, and the name “Walsingham”, suggesting the documents may have been penned by Mary, Queen of Scots.
This was confirmed by comparing them with the plain text of letters in Walsingham’s papers in the British Library and through other methods.
A search for similar letters in BnF collections uncovered 57 with the same cipher.
Commenting on the new paper, Mary Queen of Scots expert John Guy, who wrote the 2004 biography of Mary Queen of Scots, said this is the most significant find about Mary for a century.
He said: “This discovery is a literary and historical sensation. Fabulous! This is the most important new find on Mary Queen of Scots for 100 years.”
The authors suggest that other coded letters written by Mary may still be missing.