Sarah was indeed a great asset to begin with. On the wedding day, the Queen chose a particularly stunning outfit designed by her Hartnell-trained couturier, Ian Thomas. It had prompted a rare compliment from Prince Philip, who came into her dressing room during one of the fittings. According to Thomas, she had blushed with pleasure – it was a great example of the ongoing strength of their love for each other, as they approached forty years of marriage.

She may not have felt quite so happy with Prince William’s behaviour as a sailor-suited page at the wedding in Westminster Abbey. He jiggled and fiddled throughout the ceremony and the Queen kept glancing disapprovingly in his direction. She had been taught to sit still when she was far younger than the four-year-old Prince William – and to keep a straight back. As far as she could see, he had not been taught any royal discipline at all.

It was, however, an exceptionally joyful day. The Queen liked her new daughter-in-law and was delighted with the match. The feeling was mutual and Sarah often spoke of their ‘special bond’. They both loved horses, dogs, country life and of course Prince Andrew – and to this day the Queen keeps in touch with her.

The joy and cheerfulness generated by the Duke and Duchess of York’s wedding was gradually diminished as the eighties drew to end. First of all, Prince Edward dropped out of the Royal Marines in January 1987, much to the horror of his siblings, who thought they had persuaded him to stay and complete his training.

Prince Philip was extremely understanding; indeed, it was he, not the Queen, who was the more sympathetic to Edward’s decision. The royal family had a long association with this most martial of services: Edward’s grandfather George VI was Captain General of the Royal Marines, his father succeeded him and his great uncle Earl Mountbatten was Colonel Commandant up to the time he was murdered. Royal private secretaries and equerries were frequently drawn from those with a Marine background. Both Charles and Andrew had undergone commando training before they joined the Royal Navy and earned the right to wear the coveted green beret.