- Alexandra Knatchbull is daughter of Lord Brabourne, a friend of Prince Charles
- 37-year-old is the second goddaughter of the late Diana, Princess of Wales
- Marriage to Thomas in June 2016 was dubbed society wedding of the year
- Couple welcomed son Alden Peter Theodore Mountbatten, born on March 27
London-born Alexandra, 37, is the daughter of Lord and Lady Brabourne and the great granddaughter of the late Lord Mountbatten, with whom Prince Charles had an exceptionally close bond while growing up.