Not since Trotsky vanished from the Soviet politburo portrait has photo-editing caused such a storm. What dark secrets lie behind the daughter’s misaligned sweater, the blurred skirt and the twisted zip? What dynastic horror is being concealed by the Princess of Wales’s missing wedding ring? What are we not being told?

Questions over the princess’s abdominal operation follow hard on the heels of those over the king’s cancer. Both suggest something has been seriously wrong with the health of senior members of the royal family, something that they want to keep private. It has not worked. That subtlest of art forms, publicity manipulation, has gone awry. The palace must be asking, where is some nonsense from Prince Harry when we most need it?

The picture of the Princess of Wales and her children published over the weekend could hardly have been more charming and reassuring. After weeks of seclusion, she appeared smiling, hale and hearty. Good for her. If something went a bit fuzzy with the picture of her hand, so what? Her face is what matters. We can surely congratulate her on apparently being well, and turn the page.

Except that has not happened. The reality is that since the early years of Queen Elizabeth, the British royal family has validated itself through the medium of publicity. It did not follow most of Europe’s “cycling monarchies” into modesty and privacy. It did not treat its anachronistic status as purely ceremonial. The Queen presented her monarchy in full historic majesty, represented by an extended family of uncles, aunts and cousins with an estate of palaces, titles and functions, all involving serious money.

There was only one form of legitimacy in this approach: that it was popular. British royalty relied on its celebrity, promoted worldwide. Broadly speaking, it worked. The Queen, King Charles and Prince William have been ideally cast. If others didn’t follow the script – Princesses Margaret and Diana and Prince Harry – they were almost perfect foils. But to the end of time, the institution of monarchy will depend on popular support. That is why its handling of the media is crucial. Press officers are its brigade of guards.

The iron law of celebrity states that there can be no such thing as privacy. There may be sympathy. There may be understanding. But there is no secrecy. The column inches and websites, once brought to life, are aching to be filled. They ache even more today, galvanised by an undisciplined and unregulated digital media, free to pour its poison into a world where lies are cash. The social media treatment of the health of the Princess of Wales has been disgusting. That such material should be unpoliced and legal is a scandal.

The moral of the editing of the royal picture is simple. Tell all. The princess has now admitted she edited the photograph but not why or what she edited out. At this stage, privacy does not work. It breeds rumour, gossip and fabrication. When fake news and fake pictures are rampant, secrecy is the enemy of truth. Just say what the matter is. It is more likely to generate respect.

• Simon Jenkins is a Guardian columnist

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