Techniques Mary, Queen Of Scots And Elizabeth I Used To Keep Their Letters Secret Revealed


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

last letter

Mary, Queen of Scots' last letter contains marks and holes used to fold it into a shape that could not be opened without it being obvious. This is called "letterlocking". Image Credit: National Library of Scotland.

The techniques used by Mary, Queen of Scots and Elizabeth I to keep their letters secret have been revealed. In some cases, such as the last letter sent by Mary before her execution, understanding the methods used for confidentiality can improve our interpretation of the words contained therein. In other cases, it can allow us to read text hidden for centuries without damaging the primary document.

In Tudor England, keeping one's words secret could be a matter of life and death, as Mary Stuart, cousin to Queen Elizabeth, learned when the interception of one of her letters led to her trial and execution. To avoid such fates, letter writers of the era used elaborate folding techniques, known as letterlocking, so that missives could not be read without it being obvious to the ultimate recipient they had been opened in transit. Such techniques date to at least the 1390s but reached a pinnacle in the Tudor era.


A paper in Electronic British Library Journal reintroduces the world to a particularly elaborate and impressive form of letterlocking, known as the spiral lock. Among its users were Mary, Queen of Scots and Queen Elizabeth I.

Left image: The workings of the spiral-lock locking mechanism. Left: Model of the locking mechanism showing the threading sequence taken by the lock; 1–12 indicate different sections of the lock as it wraps around and passes through the slits made into the packet and itself (3, 7, and 11); X–Z indicate slits through the packet and lock. Center: Model of a closed packet using this lock (front and back). Right: Diagram of the lock indicating different folded sections. Image credit: Unlocking History Research Group archive, MC0760, MIT Libraries

Some letters have come down through history to us unopened; archivists' reluctance to damage them has left them unread. Earlier this year scientists from the Unlocking History Research Group at Queen Mary University of London (named for a different Mary) revealed an X-ray scanning technique that can read the ink inside these documents while still folded. The letters revealed at that time provided insight into the activities of the 17th-century middle class.

Other letters have survived after being opened, sometimes as prized museum exhibits. Now members of the same team are reverse-engineering these, using traces of fold lines to reconstruct the form in which they were sent.

As part of the British Library's exhibition Elizabeth and Mary: Royal Cousins, Rival Queens, these methods have been applied to surviving letters from both. The paper notes “A number of the European monarchs who used [the spiral lock] were related to and were corresponding with one another, raising the prospect that use of this letterlocking method was spread across European courts through royal correspondence.” The process wasn't easy, but both Elizabeth and Mary “Seem to have had exceptional skills at using it.”


Mary, Queen of Scots may have been undone by a letter that fell into her enemies' hands, but that didn't stop her writing others using the spiral lock thereafter. The night before her execution she wrote a letter to the French king Henry III including her final will and an effort to establish her status as a martyr to her Catholic faith. The letter is now considered a treasure of the National Library of Scotland. It contains a variation of the locking technique never reported elsewhere and possibly of Mary's own invention. The authors note the elaborate folding, requiring at least 30 precise movements, undermines historians who have presented the letter as “dashed off in a haze of weeping”.

Using a combination of comparison with similar examples and marks on the page revealed with modern lighting, the Unlocking History team reconstructed the processes used and the differences with more standard techniques.

Other examples described in detail in the paper include Queen Elizabeth's letter to Henry III in 1573 rejecting marriage to his brother, and one sent in 1570 by Catherine de’ Medici, mother of Henry and two other French kings.

The paper also provides detailed instructions on how to make a spiral lock and links to video demonstrations for those who wish to revive lost arts or have secrets to keep they don't trust to digital encryption.


  • tag
  • humans,

  • history