Christmas is a big occasion for any family, none less the Royals, but an expert on the Royal Family has now explained how Kate Middleton "puts duty before self" for the festive season.The 39 year old will be spending Christmas as Sandringham with her husband Prince William, also 39, children Prince George, eight, Princess Charlotte, six, and Prince Louis, three, as they rally around The Queen on her first Christmas without her late husband Prince Philip.