Mary, Queen of Scots

On October 1, 1569, the Duke of Norfolk was arrested by Queen Elizabeth I for conspiring to marry Mary Queen of Scots. An excerpt from the article:

"The English queen was at a loss what to do with Mary who was, on the one side, a family relation and fellow monarch with divine rights but, on the other side, a serious threat to her throne. As in many other areas of policy, Elizabeth dithered and procrastinated, delaying the ultimate decision regarding Mary's fate by putting her under house arrest. To thwart possible coups, the former Queen of Scots was regularly moved to different country houses and kept under close observation. Unfortunately for Mary, this would result in almost 20 years of imprisonment during which she saw neither Scotland or her son ever again. The two queens never met either as Mary was moved from the Scottish border to Sheffield Castle, Tutbury Castle, and Fotheringhay Castle, amongst many others. Forbidden the presence of a Catholic priest, Mary got around the prohibition by having a priest disguise himself as an almoner.
Even in confinement, Mary was a danger to Elizabeth. The former Scottish queen had become the figurehead for Catholic-inspired plots to remove Elizabeth from her throne. In 1569 CE there was a rebellion in the north of England stirred up by the earls of Northumberland and Westmorland, both staunch Catholics. The plotters took Durham and hoped to have Mary become queen and then marry Thomas Howard, the Duke of Norfolk. Elizabeth responded emphatically by sending an army led by the Earl of Sussex which caused the rebel leaders to flee in panic; 900 of the rebels were rounded up and hanged. In 1570 CE the Pope excommunicated Elizabeth for heresy following her religious reforms (the Elizabethan Religious Settlement). As a consequence of the excommunication, all Catholics were now released from any allegiance to their queen."