The spiral-locked letters of Elizabeth I and Mary, Queen of Scots

This article presents evidence about the use of the 'spiral lock', a highly secure letterlocking mechanism used by Elizabeth I, Mary, Queen of Scots, and other letter-writers in early modern Europe, to secure their correspondence shut. After explaining the concept of letterlocking, a centuries-old communication security technique, we demonstrate how the spiral lock worked, using photographs, vector drawings, and videos alongside textual descriptions, and show both how the lock was made and how to recognize it in an archive. The findings are set in multiple contexts: letterlocking as a new field of study; new digital humanities research in the life and letters of Mary, Queen of Scots; and a major exhibition at the British Library on the intersecting lives of the two queens