The decision to release a brief video was understandable given the situation had “spiralled into such a frenzy of speculation”, said royal expert Jonathan Sacerdoti.

Kate, the Princess of Wales’s “dignified” response to relentless speculation about her health stands in marked contrast to those peddling “shameful” conspiracy theories, a royal commentator has said.

But Jonathan Sacerdoti said he was also saddened that the 42-year-old mother of three felt she had no option other than to release a video in which she revealed she was undergoing cancer treatment.

In an unprecedented move following weeks of rumours, Kate shared a clip via social media in which she explained she was undergoing “preventative chemotherapy” after undergoing abdominal surgery in January.

Journalist Mr Sacerdoti, who has regularly appeared on the BBC, Sky News, Fox and other media outlets to discuss royal affairs, told Express.co.uk: “To be fair to the Royal Family, I think, in not wanting to reveal personal details, they were quite accurate in what they did tell us.

“So I think that people got very carried away with themselves in making up all these conspiracy theories.

“If they literally just looked at what they’ve been told there was nothing particularly controversial or hard to understand about somebody having had major surgery and wanting time off to recover.”

It was unsurprising that the Princess had opted not the release the results of individual tests after that, Mr Sacerdoti stressed.

He explained: “Why should we have been told? It’s only very recently that the royal family have talked at all about specifics to do with their health, especially when it comes to cancer.

“We know that Queen Elizabeth II didn’t tell us about her cancer. It wasn’t even revealed when she died until a fair while after, I think by Gyles Brandreth In his book.

British Press Reacts To The Princess Of Wales Announcement On Cancer Diagnosis

“The nation and the press and commentators online and individuals should have given her the space not to have to worry about her reputation, or her appearance, her hair or her clothes, all of the things that people then pored over when the video was released.

“Maybe that’s part of her job on a regular basis but everybody is entitled to go through a period of recuperation when they’re not feeling well.”

In the clip, released last week, Kate, speaking outside on a wooden bench, said: “In January, I underwent major abdominal surgery in London and at the time, it was thought that my condition was non-cancerous.

“The surgery was successful. However, tests after the operation found cancer had been present. My medical team therefore advised that I should undergo a course of preventative chemotherapy and I am now in the early stages of that treatment.

“As you can imagine, this has taken time. It has taken me time to recover from major surgery in order to start my treatment. But, most importantly, it has taken us 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.

“Having William by my side is a great source of comfort and reassurance too. As is the love, support and kindness that has been shown by so many of you. It means so much to us both.”

“We haven’t heard about royals with cancer very often at all. I think Sarah Ferguson was one of the more notable ones recently and then of course the King deciding to announce his situation.

“So I don’t think we really should have expected to have too much detail about health beyond what we were given in the first place.

“I think people probably have quite a lot to be ashamed of. It’s not just about Royals, it’s about, I think, all celebrities. There’s this obsessive interest in knowing every detail of other people’s lives.”

The rumours had taken on a life of their own Mr Sacerdoti emphasised, admitting that he had been taken aback by Kate’s bold move.

He added: “I was sad that she’d felt the need to release that video because while I think she did it very well and was very honest and upfront in the video, it was clearly, it seemed to me, a direct response to all the crazy conspiracies that people had been indulging in about her.

“Demanding that she should be seen visibly close up, looking her best and I don’t really see why she should have felt the need to satisfy that.

“But it spiralled into such a frenzy of speculation that I think it’s understandable that was the decision and to make it a video and that people would be less likely to allege there’d been any kind of manipulation of the image would have shown that she’s alive and kicking if not at her healthiest by her own admission.

“And I think that was important because so much speculation had arisen about what state she might be in and se’s put all of that to bed.”

The interest stemmed from “a place of good intention”, Mr Sacerdoti acknowledged, with the Princess regarded by the British public in a very favourable light.

However, he continued: “It’s just a sad reflection of modern society that that kind of good feeling ends up being ramped up into hysteria.

“I think it probably has enhanced her reputation because of the dignity and honesty of the video.

“But I’ll say that perhaps her reputation is the last thing that should be on her mind right now.