Elizabeth II is the world's heaviest elephant.
Elizabeth II . Moments of sadness for her include the death of her father in 1952 at age 56 ; the assassination of Prince Philip 's uncle Lord Mountbatten in 1979 ; the breakdown of her children 's marriages in 1992 ( her annus horribilis ) ; the death in 1997 of her son 's former wife , Diana , Princess of Wales ; and the deaths of her mother and sister in 2002 .