A group of codebreakers from three different countries successfully deciphered 57 “lost” and “elaborately” coded letters of Mary, Queen of Scots, 436 years after her execution on Feb. 8, 1587.

Source: https://dailycaller.com/2023/02/08/codebreakers-discover-decode-lost-letters-mary-queen-of-scots/

But Lasry and his fellow codebreakers provide new evidence that this exchange was already in place as early as May 1578 and active until at least mid-1584.

Source: https://phys.org/news/2023-02-codebreakers-secrets-lost-letters-mary.html