"Margaret Thatcher, Britain's 'Iron Lady' Prime Minister, has died. The first woman ever to serve as prime minister of Great Britain and the longest-serving British prime minister of the 20th century has died at age 87. ""It is with great sadness that Mark and Carol Thatcher announced that their mother Baroness Thatcher died peacefully following a stroke this morning."" Lord Timothy Bell said today. Margaret Thatcher poses for a portrait, circa 1990. (Terry O'Neill/Hulton Archive/Getty Images)"