• Stewart Pearce, Princess Diana's former voice coach, weighed in on Prince Harry's upcoming memoir
  • The royal author noted that Harry "is so much like his mother" and "moves on instinct just as she did"
  • Pearce suggested that Harry's book is unlikely to contain any digs at the royal family

Prince Harry would have had his mom Princess Diana's approval in releasing a memoir if she were alive, a royal expert has claimed.

Stewart Pearce, Princess Diana's former voice coach and author of "Diana: The Voice of Change," recently weighed in on Prince Harry's announcement that he will be publishing his memoir next year and suggested that the late Princess of Wales would have "completely" supported her son's move.

"Harry is so much like his mother in the sense that he has an impetuosity," he told Us Weekly Tuesday. "He moves on instinct just as she did."

Pearce, who knew Princess Diana before she died in 1997, went on to say that he believes the late royal's interviews with Andrew Morton and Martin Bashir were enough proof that she would support the truth coming out.

"Diana was gleeful about the statements that she made during those interviews. Sometimes I would say, 'Are you really going to engage yourself in that?' … And she'd say, 'Yeah, I've got to!' and would do it," he added.

When it comes to the potential content of Prince Harry's memoir, Pearce doubts that it will include any digs at the royal family. "There won’t be anything in terms of accusation, not at all. He’s in a situation of transformation," he said.

Despite this, the royal author suggested that the royal family would "probably [be] feeling slightly anxious" over Prince Harry's book.

Pearce is not the only one who thinks that way about how the royal family may be feeling about Prince Harry's decision to publish a memoir. An unnamed source told Us Weekly shortly after the Duke of Sussex's announcement that the members of the royal family were concerned and were not prepared for his book and what he might share in it.

"The royal family is shaken up about the book," the source told the outlet. 

Prince Charles and Prince William were "particularly concerned about what Prince Harry will reveal," the insider added, especially after the streak of criticisms against the Prince of Wales that were "bad enough."

Last month, Prince Harry announced that he was writing a memoir, which he described as "a firsthand account of my life that’s accurate and wholly truthful."

"I’m writing this not as the prince I was born but as the man I have become," he wrote in a statement obtained by Us Weekly. "I’ve worn many hats over the years, both literally and figuratively, and my hope is that in telling my story — the highs and lows, the mistakes, the lessons learned — I can help show that no matter where we come from, we have more in common than we think."

Princess Diana with William and Harry Princess Diana, Princess of Wales with her sons Prince William and Prince Harry attend the Heads of State VE Remembrance Service in Hyde Park on May 7, 1995 in London. Photo: Anwar Hussein/Getty Images