When she met Prince William, the heir to the British throne, more than 20 years ago at St Andrews University, Catherine, the Princess of Wales had her first taste of the appetite for news about her life and her budding romantic involvement with the young prince.

Since their marriage in 2011, the desire for news, any news, about Catherine has only grown. Her every movement has been tracked, every outfit remarked upon, every decision – around her work, her children, the way she spends her free time, the way she moves – has been endlessly analysed, assessed, lauded or judged.

The most famous woman in the UK is, one imagines, used to the attention – even if it is endured, rather than enjoyed. But it is unlikely that anything can have prepared her, and those who love her, for the 24-hour a day, seven days a week onslaught of speculation that the princess has faced since it was announced in January that she had undergone abdominal surgery.

Catherine and William have tried to keep this very personal, intensely difficult time for their family private. But that was made impossible by the tornado of rumours and conspiracy theories reaching incredible force – in the traditional press, digital media and on social media.

In a recorded message on Friday, Catherine revealed she has been diagnosed with cancer and is in the early stages of receiving chemotherapy treatment. Learning, after tests, that cancer had been present had come as a “huge shock”, she said. She added that it had taken time to process, time for her to recover in order to start her treatment and, most importantly, “time to explain everything to George, Charlotte and Louis in a way that is appropriate for them, and to reassure them that I am going to be OK”.

In that time between the princess being admitted to the London Clinic on 16 January and Friday’s announcement, speculation about her condition took on a life of its own. It reached fever pitch after the first official photograph of Catherine to be released after her surgery was recalled by some of the world’s biggest picture agencies over claims it had been manipulated.

Her public apology for the “confusion”, which she said was caused by her digital editing of the Mother’s Day family photograph, did not still the waters. It was only when footage was published by the Sun of her smiling alongside her husband during a visit to a farm shop in Windsor that some resemblance of sanity – at least in the mainstream media – appeared to reemerge.

But even that appeared to do little to stem the unhinged theories that have abounded about Catherine and her husband on social media. On X, the influence of its “free speech absolutist” owner Elon Musk has been palpable. Among the more publishable conspiracies are the insistence that the footage of the princess was a body double, or that she was in a coma, or recovering from plastic surgery or was, in fact, dead.

Meanwhile the Sun’s tabloid rival the Daily Mirror has also published a variety of exclusives, such as “Kate Middleton lookalike ‘was at work’ when farm shop video was shot as conspiracy theories swirl’, and “Kate Middleton clip sparks social media meltdown with jokes and conspiracies.”

The speculation has, at least, provided a fig leaf for much of the traditional media to write incessantly about the situation, often under the guise of saying the princess should be left alone. The Sun, which this week faced accusations of “overwhelming intrusion” from Catherine’s brother-in-law Prince Harry in a high court hearing, last week printed a front page message to “all the social media trolls, idiotic conspiracy theorists and sniping media critics: Lay off Kate”.

Its editor, Victoria Newton, told Times Radio that “crazy online speculation” had gone “out of control”, adding: “It seemed that the public were really really desperate to know what was wrong with her but I think she had a right to be at home recuperating.”

Days later it published the footage of her farm shop visit.

While news of the princess’s diagnosis may induce a pang of guilt in those who have enjoyed gorging on the most lurid speculation, it is unlikely to result in a reduction of content about her.

The palace has stressed that Catherine “has a right to medical privacy, as we all do”. And it is right. But perhaps, like King Canute who recognised his lack of dominion in the face of incoming waves, they know that in some areas of the media – let alone the more unhinged corners of the internet – it is a plea likely to fall on deaf ears.