It was intercepted by Elizabeth's spymaster Francis Walsingham and therefore Elizabeth had no choice but the have Mary tried for treason on the 14th of October 1586, she was condemned to death eleven days later.
Cecil knew that as a queen it would be difficult to have Mary executed, to most people, her royal rank would have excused her from any blame, it would be asked 'Would an anointed queen plan the murder of another anointed queen?' Cecil knew this all too well, she was condemned to death as "Mary Stuart, commonly called Queen of Scotland". Elizabeth too had a problem with queen-ship, she could not bring herself to execute a reigning queen and put off signing the death warrant. The signing of the death warrant is another incident in the death of Mary that is questioned. Did Elizabeth sign of her own choice or was she tricked by William Cecil? Either way sign it she did and Mary went to her death on this day in February 1587 at Fotheringhay Castle.
Evidence had been found to convict Mary, it was the cause of the sad end to a life that had been full of tragedies and more than a few foolish actions.