The Princess of Wales' father and mother Michael and Carole Middleton are an ordinary middle-class couple in an extraordinary position. As parents-in-law to Prince William and grandparents to Prince George, they have unprecedented influence on two future kings. At a time when the royal family is in turmoil, with Andrew having his royal titles taken away, this programme examines a possible role for the Middletons, asking if membership of the royal family could ever be based not just on birthright or marriage, but on meritocracy or virtue