That letter was part of the Babington Plot—a scheme to assassinate Queen Elizabeth and place Mary on the English throne. But Mary did not know that every word she wrote was being read by Sir Francis Walsingham, Elizabeth's spymaster, who had intercepted the correspondence and broken the cipher. Full video — The Letter That Toppled a Royal House: https://www.youtube.com/watch?v=dHR7claRDGQ




