How Kate Middleton and Prince William Feel About the Rumors Surrounding Them: Royal Expert (Exclusive)

From a so-called lookalike to a possible breach of Kate's records, the royal couple's been dealing with a lot as of late.

Kate Middleton and Prince William are feeling shock, anger, disbelief and frustration amid wild, over-the-top speculation and vast conspiracy theories with regard to her whereabouts and recovery progress from abdominal surgery.

ET spoke with royal expert Katie Nicholl about how the Prince and Princess of Wales are feeling about the swirling rumors centered around them. Nicholl tells ET that the royal couple is astute enough to understand how social media works in this day and age, but the constant attention is, plainly put, getting to them.

"Well, I know from the sources that I've spoken to that both William and Kate have been pretty shocked and genuinely surprised by the wild rumors that are circulating on the internet," Nicholl tells ET. "I think there's a sense of frustration, possibly even anger, certainly on William's part."

For his part, not only has William had to look after his wife, who is still recovering from abdominal surgery, but also the couple's three young children -- Prince George, 10, Princess Charlotte, 8, and Prince Louis, 5. On top of that, William is also trying to tune out the deafening noise, including unsubstantiated claims running rampant online and elsewhere.

"I think the suggestions that [Kate's] had, well, anything as crazy as a bad haircut that she's needed to grow out to cosmetic surgery that's gone wrong or people speculating that possibly she's in a coma, I think that has made the Prince of Wales frustrated, upset and pretty angry as well," Nicholl says. "It's been difficult for them. I think they're trying to ignore as much as they can. But, of course, this is a couple who have had to embrace social media. They've got an Instagram handle, they've got hundreds of thousands of followers. They certainly don't have their heads in the sand. They are aware of what is being written and what is being said. And I think there's a sense of frustration that they can't bring an end to it."

Kate Middleton, Prince William and their children in 2023. - Chris Jackson/Getty Images

The sad reality, Nicholl adds, is that the couple is likely very aware that the noise is not going to end. Not until the public can see with their own eyes that Kate is "back to her normal, happy, healthy self."

Which is what makes the video footage obtained by TMZ of Kate and William a mile from their Windsor home all the more frustrating.

"The TMZ video really should have quashed all of the fevered speculation about the Princess of Wales," Nicholl explains. "Her health, her recovery, and it simply hasn't. You would have thought that the video, which showed her walking at quite a brisk pace, carrying a shopping bag, looking pretty healthy and happy, and chatting in a very relaxed way with her husband, would have just dampened out all of the rife speculation that has really been circulating on the internet for weeks now. But, unbelievably, many of those theories are still circulating on the internet."

The wild speculation includes that there was a body double -- a rumor and conspiracy theory that prompted a Kate lookalike to speak out about it.

Kate Middleton and Prince William during less hectic times. - Chris Jackson/Getty Images

"People think that I'm Kate Middleton in the video that's come out online," said Heidi Egan, a British woman known for her resemblance of Kate. "Given my alibi that, no, it wasn't me in the video. I was actually at work."

And as if the royal couple didn't already have enough to deal with, police are now looking into a possible breach of Kate's health records, a U.K. health minister announced, after the U.K. tabloid The Mirror reported that The London Clinic -- where Kate was treated in January for a "planned abdominal surgery" -- has launched an investigation over claims that staff tried to access her private medical records. The Information Commissioner's Office, Britain's data watchdog, released a statement confirming that they are looking into the potential breach. 

The potential breach of her medical records will be handled swiftly, not just because it may have targeted the Princess of Wales, but because privacy laws are extremely strict in the U.K. But underscoring the seriousness of the situation is the fact that The London Clinic is equivalent to Cedars-Sinai in Los Angeles or New York-Presbyterian Hospital, two world-class facilities favored by the rich and famous.

"The London Clinic will be doing everything it can to assure its patients, many of whom are high profile," says Nicholl while referencing former U.K. Prime Minster David Cameron, who was born at that hospital. Former U.S. President John F. Kennedy Jr. also was treated there, as are many royals, celebrities and VIPs who insist on discretion even more so.

"The big challenge here is for The London Clinic and maintaining its standards and its reputation as being one of the most discreet clinics in London, when clearly there was a major security breach attempted during Katherine's stay," Nicholl says.

The potential breach is reminiscent of a 2012 incident, when Australian pranksters managed to get patched through to Kate's doctors amid her receiving treatment for severe nausea and vomiting at London's King Edward VII Hospital while she was pregnant with Prince George.

While the prank only resulted in the pranksters getting transferred to Kate's doctors, that ordeal ended in tragedy, when the nurse who transferred the call took her own life in 2014.