King Charles and Prince William 'Very Wary' of Prince Harry's Testimony During Tabloid Court Appearance: Source

Prince Harry might have more secrets to spill!

This week, the Duke of Sussex has been testifying at the High Court in London in a case against the Mirror Group Newspapers tabloid. On Wednesday, June 7, Harry spoke against the publication, discussing how their stories have negatively affected his life.

Following his court appearance, royal expert Katie Nicholl divulged that the prince's father and brother were stressed about what he might say on the stand.

"My sources tell me that [King Charles III] and [Prince William] were very wary about Harry going into the witness box," Nicholl shared. "I think when you see what came out of Harry's evidence and his witness statement, you can understand why."

In the father-of-two's written testimony, he discussed a rumor many news outlets started about Charles' paternity. The articles claimed Princess Diana's ex, Major James Hewitt, was in fact Harry's father, not Charles.

"Numerous newspapers had reported a rumor that my biological father was James Hewitt, a man my mother had a relationship with after I was born," the red-haired royal said. "At the time of this article and others similar to it, I wasn't actually aware that my mother hadn't met Major Hewitt until after I was born."

"I remember on multiple occasions hearing a voicemail for the first time that wasn't new – I would simply put it down to perhaps a technical glitch... or even just having too many drinks the night before and having forgotten that I'd listened to it," he added about the tabloid potentially tapping his phone. "I also distinctly remember people saying to me 'Did you not get my voicemail?'. I was like, 'No', and sometimes I would go back into my voicemail to look for it, but still couldn't find it."

As the six-week trial carries on, Nicholl said Harry could reveal "details that the royal family really don't want to come out."

As OK! previously reported, Nicholl was not the first expert to express the brood's concern for Harry's remarks.

"It has his family terrified," a royal insider said about the Spare author's then upcoming statements. "They are nervous about what Harry could ultimately reveal, and rightly so. His book was bad enough."

They then referenced Harry's claims that Charles and Camilla gave stories to the press about he and Meghan Markle in exchange for positive press about themselves.

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"He could elaborate more on the story, planting claims in court," the source added. "Was the whole family leaking dirt on Harry and Meghan to keep the spotlight off themselves?"

"Harry is having his day in court, and no one in the royal family is looking forward to it," the insider continued. "They are all extremely nervous about what he'll say."

ET reported on Nicholl's comments.