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Kristen Stewart received a Golden Globe nomination for her portrayal of Princess Diana in "Spencer" – but not everyone was convinced by her performance.

"Kristen is a fine artist, but the portrayal that she brings has nothing to do with Diana," the late royal’s voice coach Stewart Pearce told Fox News. "It doesn’t look like Diana or sound like Diana. It doesn’t have the same flow, grace, or elegance Diana had. What Kristen did is develop a mannered performance where everything is staccato. This was not fundamentally at all part of Diana’s nature. Everything about her was smooth."

The film, directed by Pablo Larraín, focuses on a Christmas weekend the Princess of Wales had with the royal family that preceded her divorce from Prince Charles. It has made Stewart, 31, for the first time in her career a front-runner for a best actress Oscar nomination.

"Pablo is obviously fascinated in the hidden truth and the trauma of the feminine," Pearce shared. "But his perspective is based very loosely on a series of ideas that he picked up… Artists are certainly entitled to their own perceptions, but if you’re going to deal with a biopic about a renowned, iconic world figure who brought about the extraordinary changes that Diana brought about, then I feel an attention to detail is essential."

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"The story felt surreal," he continued. "While Diana experience great turmoil, she also experienced great triumphs. But in ‘Spencer,’ there’s no redemption. It’s just horror, horror, horror. Maybe that’s what Pablo wanted to create, but it’s not the Diana I knew."

Pearce, who worked with Margaret Thatcher and the Royal Shakespeare Company before he befriended the Princess of Wales, recently wrote a book about their work together titled "Diana: The Voice of Change." It explores her life principles and how she became "a force of liberation" as a royal before her untimely death in 1997 at age 36.

While Pearce wasn’t impressed by Stewart’s portrayal, there was one actress who earned his praise. He said Emma Corrin’s interpretation as a young Diana in Netflix’s "The Crown" was "pure delight."

"The way she shaped her body, the way she shaped her voice, the way she breathed, the way she moved – they were all completely in congruence with what Diana was all about," said Pearce. "She did her homework. What Kristen did was reduce her to a caricature rather than stretching herself as an artist."

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Princess Diana

Princess Diana passed away from injuries she sustained in a Paris car crash. She was 36. ( AP Photo/Jim Bourdier )

Pearce said he isn’t surprised that "Spencer" touches on Diana’s marriage to Charles as "it’s part of the story."

"It’s a very unique story," said Pearce. "And there are aspects of her life that many people don’t understand. And the truth is she loved Prince Charles and he didn’t love her. So she had to find space for her passion. But there was more to Diana. She was one of the most quick-witted, joyous beings that I’ve ever had the great honor and pleasure to know and work with."

"She was an extraordinarily, beautiful young woman who wanted to experience the vitality of life," he continued. "She was happy [in her final] years. She met Dodi Fayed, a gentle, loving human being with exquisite manners who really wanted to look after her and protect her. She was very, very happy. Was she in love with him? I don’t think so. She didn’t talk about being in love. She was just having a wonderful time. There was more to her story."

Pearce first met Diana in November 1995 and they remained connected until her death.

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Emma Corrin

Josh O’Connor and Emma Corrin star as Prince Charles and Princess Diana in 'The Crown.' (Netflix    )

"She was an ordinary human being, but her iconic status made her extraordinary," he said. "The first thing Diana wanted to do when she came to see me in my studio in London was to do some washing up. She wanted to get grounded and clean because that’s what made her tick. She loved cleaning. And she loved having great fun."

Pearce said he isn’t surprised that Hollywood continues to be fascinated by Diana. However, he hopes that other elements of her life, and who she was, will eventually be explored on the big screen.

"There’s a tremendous amount of information on Diana that’s out there," he said. "The difficulty is that, of course, we all have a perception of who Diana was."

Back in July, on what would have been Diana’s 60th birthday, Pearce recalled his favorite memory of the princess.

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Princess Diana

Diana, Princess of Wales, has been the subject of several projects in Hollywood. (Tim Graham Photo Library via Getty Images)

"Whenever she arrived for a session, she would always say to me, ‘Do you have any washing up?’" Pearce chuckled at the time. "I do mean washing China or crockery. It was her way of becoming grounded and ordinary. Before she married Prince Charles, she lived in an apartment with three girlfriends. She loved house cleaning. She absolutely loved it. I would laugh whenever a guest came by and I provided them tea. Because I remember Diana coming in and saying, ‘Can I do any washing?’ She would say to me, ‘Can I iron any of your shirts?’ She loved ironing. I would tell her, ‘Darling really, no, I can’t have you ironing my shirts, but I will leave the China for you to wash up.’"

"We would laugh a lot," Pearce shared. "She was just so much fun and could be really naughty with her humor. It was never at anybody’s expense, but we would laugh so much that sometimes we would even forget what we were laughing about. And you couldn’t help but laugh because that laugh of hers was just so infectious."

The Associated Press contributed to this report.