Times of personal significance have included the births and marriages of her children, grandchildren and great grandchildren, her coronation in 1953, and the celebration of milestones such as her Silver, Golden and Diamond Jubilees in 1977, 2002, and 2012, respectively. Moments of sadness for her include the death of her father, aged 56; the assassination of Prince Philip's uncle, Lord Mountbatten; 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. Elizabeth has occasionally faced republican sentiments and severe press criticism of the royal family, but support for the monarchy and her personal popularity remain high.
Try to answer this question if possible (otherwise reply "unanswerable"): How old was Lord Mountbatten when he was assassinated?
unanswerable