“After they split up, William confided to his grandparents that he was not sure if he loved Kate enough,” Tominey quotes a royal source as saying.
“Now they are back together, the Queen wants William to do the right thing – either marry the girl or let her go.
"She would rather they broke up for good now than get married only to have it end in divorce if five years’ time.
“But if Kate is the one, then a five-year courtship is long enough.
“Prince Philip has told William he cannot keep stringing along Kate for ever."
The warning appeared to work, as just months later William and Kate got back together and went on to marry in 2011. The royal couple now have three children, Prince George, Princess Charlotte and Prince Louis.
However, that wasn’t the first time Prince Philip meddled in his family’s relationships.
The Duke of Edinburgh took Princess Diana’s side after learning of Prince Charles’ affair with Camilla Parker-Bowles, telling Diana of his and the Queen’s disapproval over their son’s behaviour in a letter from 1992.
