The document examines the Lambert Simnel rebellion against King Henry VII in 1487 and the extent to which it threatened Henry's authority. It discusses how pretenders were possible due to Henry usurping the throne and the mystery around the Princes in the Tower. Lambert Simnel, a young boy, was passed off as Edward Plantagenet, Earl of Warwick. He gained support from Ireland and Margaret of Burgundy. Henry initially seemed unaware until early 1487. Henry crushed the rebellion by exhibiting the real Earl of Warwick and defeating Simnel's army at the Battle of Stoke. The rebellion threatened Henry's authority through an invasion force with foreign support and nobility backing Simnel.