Ken Wharfe also shares how Kristen Stewart’s performance as Princess Diana rates against his experience with the Princess of Wales

Kristen Stewart in “Spencer”; Princess Diana. Photo: Neon; Getty

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Kristen Stewart in “Spencer”; Princess Diana. Neon; Getty

Ken Wharfe, who was Princess Diana’s bodyguard in the late 1980s and early 1990s, joined the royal family for the Christmas holiday celebrations at Sandringham that provide the backdrop for Pablo Larraín’s Spencer.

“It was purgatory for her,” Wharfe tells PEOPLE in this week’s issue.

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Kristen Stewart in Spencer; Princess Diana. Neon; Julian Parker/Getty

According to Wharfe, the Princess of Wales “confined herself to spending time in the kitchen with the chef or with people like me, in the hope that time would while away, and she could get back to London.”

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Kristen Stewart in Spencer; Princess Diana. Neon; Anwar Hussein/Getty

Royal biographer Ingrid Seward, a journalist with whom Princess Diana was friendly, confirms that Diana hid her struggles during royal family gatherings.

“She would have put on a good front for the Queen and the family,” said Seward. “She was a properly brought-up girl and would have considered it rude to make a scene or a spectacle of herself.”

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Kristen Stewart in Spencer; Princess Diana. Neon; Nils Jorgensen/Shutterstock

Spencer does exercise some dramatic license, though, including one surprising scene featuring a heart-to-heart between Princess Diana and her dresser, played in the film by Sally Hawkins.

“From my experience, Diana never once confided in her dressers,” recalled Wharfe.

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Kristen Stewart in Spencer; Princess Diana. Neon; Getty

Wharfe praised Kristen Stewart’s portrayal of the late royal: “Out of all the people who have played Diana over the past 10 years, she’s the closest to her,” he said. “She managed to perfect her mannerisms.”