Elizabeth was protestant and heirless making many think her not fit for the English throne. Her cousin Mary, Queen of Scots was the granddaughter of Margaret Tudor, princess of England, and sister of Henry VIII, many preferred Mary to Elizabeth as Queen. Elizabeth, threatened by Mary, had her imprisoned. The imprisonment lasted 19 years, in which Mary was part of many plots to kill Elizabeth. After gaining proof of Mary’s involvement in these plots Elizabeth had her beheaded in 1567.