Then, the following month, Princess Anne and Captain Mark Phillips were finally divorced. If all of that was bad, worse was to come as, in June 1992, the Sunday Times began to serialise Andrew Morton’s book Diana: Her True Story. The Queen and Philip were at Windsor that weekend and were stunned by what they read. They were aware of how unhappy their daughter in-law was, but they never thought for one moment she would resort to airing her dirty linen in such a public way. Their whole royal life was based on obligation, discretion and duty. Prince Philip had tried to help and had written to Diana saying he wished ‘to do my utmost to help you and Charles to the best of my ability. But I am quite ready to concede that I have no talent as a marriage counsellor!’ It was to no avail; it was too little too late.

The tension was there for all to see when Diana attended Royal Ascot with the rest of the family as the second instalment of Morton’s revelations was rolling off the press. Prince Philip snubbed Diana in full view of all the top-hatted people in the royal enclosure. But at least she was there – the Duchess of York was in social Siberia.

With all three of the Queen’s children’s marriages in trouble, it seemed things could not get worse – but they did. That summer, there was nothing even her loyal husband could do when photographs of Sarah, topless in the South of France having her toes sucked by her financial adviser John Bryan, appeared in the Daily Mirror. She was staying at Balmoral with the family when that fatal nail was driven into the coffin of what was left of her reputation. The Queen was ‘furious’, as the duchess recalled. She was cold and abrupt as she berated her semi-detached daughter-in-law for exposing the monarchy to such ridicule. Prince Philip was even more direct, likening her to Edwina Mountbatten, whose morals had long been a source of embarrassment to the royal family. He said to her: ‘You should get to a nunnery – or a madhouse.’