Margaret was born at Harbottle Castle, Northumberland. Because of her nearness to the English crown, Lady Margaret Douglas was brought up chiefly at the English court in close association with the future queen Mary I of England, who remained her fast friend throughout life. She was high in the favour of her uncle, King Henry VIII of England, but was twice disgraced; first for an attachment to Lord Thomas Howard, who died in the Tower of London in 1537, and again in 1541 for a similar affair with Sir Charles Howard, brother of Queen Catherine Howard. In 1544 she married a Scottish exile, Matthew Stewart, 4th Earl of Lennox (1516-1571), who was regent of Scotland in 1570-157I. During Mary's reign, the countess of Lennox had rooms in Westminster Palace; but on the accession of Elizabeth I, she moved to Yorkshire, where her home at Temple Newsam became a centre for Roman Catholic intrigue. She succeeded in marrying off her son Henry Stewart, Lord Darnley, to Mary I of Scotland. In 1566 she was sent to the Tower, but after the murder of Darnley in 1567 she was released. She denounced Mary, but was eventually reconciled with her daughter-in-law. In 1574 she again aroused Elizabeth's anger by the marriage of her other son, Charles, Earl of Lennox, with Elizabeth Cavendish, daughter of the Earl of Shrewsbury. She was sent to the Tower with Lady Shrewsbury, but was pardoned after her son's death in 1577. Her diplomacy largely contributed to the future succession of her grandson, James VI of Scotland, to the English throne.
The Lennox jewel, made for Lady Lennox as a memento of her husband, was bought by Queen Victoria in 1842.
Updated from 1911 Encyclopedia Britannica