Margaret was appointed governess to the young Princess Mary, later Queen Mary I of England. However, at the time of the divorce of Mary's mother, Katherine of Aragon, the countess made the mistake of appearing to side with Katherine and Mary against the king, and this was his cue to declare her a traitor. She lost her titles in 1539, following the execution for treason of her eldest son, Henry Pole, Marquess of Montagu.
Eventually she was executed -- on May 27 1541 in the Tower of London -- by Henry VIII in continuation of his father's program of eliminating possible contenders for the throne. The Countess of Salisbury's execution was a memorable event, as the elderly woman did not go willingly and had to be chased around the block by the executioner. She and her husband Richard Pole had one daughter and four sons, one of whom, Reginald, became Archbishop of Canterbury.