The plotter: In 1586, a rich young Catholic names Anthony Babington planned to kill Elizabeth, rescue Mary and place her on the throne.
The plot: Babington needed to know if Mary supported his plan. He managed to get Mary's servants to hide coded messages within her beer barrels that were sent to her room. The messages reached Mary and she replied, giving her backing to the plot
The plot uncovered: Unfortunately for Mary, the servants were spied for Sir Francis Walsingham, Elizabeth's spymaster. The original message and Mary's reply were decoded and taken straight to Elizabeth. It was clear that Mary was plotting to kill the queen
The aftermath: With such clear evidence, Elizabeth had little choice but to act. Although still hesitant, she order that Mary should go on trial for treason