Secret letters written by Mary, Queen of Scots, deciphered by codebreakers solving a 500-year-old mystery

For centuries, the story of Mary, Queen of Scots, has been the subject of much debate and speculation, with her life portrayed in numerous movies and books. But on Wednesday, an international team of codebreakers announced the discovery of the long-lost secret letters of the 16th-century monarch, the most significant discovery about the Scottish queen in a century. The three codebreakers, members of the DECRYPT Project, an international, cross-disciplinary team scouring the world's archives to find coded historical documents to decipher, found more than fifty of Mary's letters containing around fifty thousand never-before-seen words. They were trawling through the digitized archive of France's national library, known as the BnF (The Bibliothèque nationale de France) when they stumbled onto enciphered documents labeled as being from Italy in the first half of the 16th century.

The letters were written by Mary Stuart when she was imprisoned in England due to the perceived threat she posed to her Protestant cousin Queen Elizabeth I. Mary, a Catholic, wrote the coded letters from 1578 to 1584. The trio realized the text was written in French and used feminine forms, indicating a woman. Phrases like "my liberty" and "my son" suggested it was an imprisoned mother. Then came the breakthrough word: "Walsingham". Francis Walsingham was Elizabeth I's principal secretary and "spymaster".

The letters show Mary diplomatically pleading her case, gossiping, complaining of illnesses and perceived antagonists and expressing distress when her son, King James VI of Scotland, was abducted. Eight of the fifty-seven letters found by the codebreakers were already in Britain's archives because Walsingham had a spy in the French embassy from mid-1583.

Historians have praised both the code-breaking and historical research of the trio, expressing keenness to get stuck into the letters. John Guy, a British historian who wrote a Mary Stuart biography, described the discovery as a "literary and historical sensation". Steven Reid, a Scottish history expert at Glasgow University, said it was "the largest discovery of new Marian evidence in the modern era". Nadine Akkerman, a professor of early modern literature at Leiden University in the Netherlands, said it was "like uncovering buried treasure" for historians.

The discovery of Mary's letters is of great significance not only to historians but also to those interested in the story of her life. It is likely to alter existing biographies of Mary's life and could help produce more accurate versions of her other coded letters. Furthermore, some of Mary's letters are still believed to be missing, with the researchers saying a physical inspection of the BnF's undigitised stock of original documents could be next.