Christopher Andersen believes there’s a reason why King Charles is "one of the most eccentric sovereigns Great Britain has ever had."

The author has written a new book about the monarch, titled "The King: The Life of Charles III." Andersen, who has previously written books about the British royal family, spoke to numerous palace insiders who have made shocking revelations about the 73-year-old.

"So much about Charles you could really trace back to his childhood, which was heartbreakingly lonely," Andersen recently claimed to ETOnline. "Charles has described his relationship with his mother [by saying] that she was cold and aloof, that his father was a bully who hectored him, who made him cry in front of other people, physically bullied him."

"I think it’s very telling that Charles only spent as a boy … two 15-minute periods a day [with his parents]," Andersen alleged. "… When he had a tonsillectomy, when he had a very bad case of the flu, when he fell down the stairs and broke his ankle, when he had an emergency appendectomy at the age of 13, neither his mother nor his father visited him at the hospital."

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Queen Elizabeth II with Prince Charles at Windsor Great Park

Queen Elizabeth II with Prince Charles at Windsor Great Park, during a polo match, 1956. Author Christopher Andersen alleged that the future king described his mother as ‘cold and aloof’ during his ‘lonely’ childhood. (Photo by Hulton Archive/Getty Images)

Andersen pointed out that Charles was sent to boarding school in Scotland, an experience that was described as "pure hell."

"What he went through is really quite alarming," said Andersen. "As a boy, as a young man, he was routinely beaten by older students, hung up naked in a shower and sprayed with cold water and left there. He was pummeled and wrestled to the ground."

"He wrote these pleading letters to his parents to please take him out of school," Andersen claimed to the outlet. "By today’s standards, it would be akin to hazing or child abuse, frankly, and yet his parents turned a blind eye to it. I think that caused a tremendous resentment."

On Wednesday night, a former classmate of Charles’ spoke out in the ITV documentary "Charles: Our New King."

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Charles arrives at Gordonstoun School

Prince Charles arrives at Gordonstoun School in Scotland for his first term. One former classmate said the future king was bullied during his time at the prestigious boarding school. (Photo by Central Press/Getty Images)

In it, he alleged that Charles was tormented while attending Gordonstoun, a boarding school in Scotland. The future king followed in his father’s footsteps and attended the school from the age of 13.

"One of the mistakes that were made when Charles arrived at Gordonstoun was that we were all told he was just to be treated like everybody else," said John Stonborough. "But he wasn’t everybody else, was he? He was going to be the King of England."

"He had a private detective, we didn’t have private detectives," he alleged. "And when he came, they strengthened all of the rules, and it became a stricter school, and I think that some people took it out on him. I actually witnessed one straight attack on Prince Charles during a rugby game when … one guy pulled his ear, and another guy punched him. And there was a little bit of pride that somehow these people managed to clock the future King of England."

Stonborough said that Charles never complained and just "put up with it."

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Queen Elizabeth sitting on the throne with King Charles

Queen Elizabeth II and Prince Charles, during the State Opening of Parliament at the Palace of Westminster on October 14, 2019, in London, England. The queen passed away on Sept. 8 at age 96. (Photo by Paul Edwards  - WPA Pool/Getty Images)

"He found it difficult to make friends … people found it difficult to make friends with him because they got teased if they tried to be his friend," said Stonborough.… But you know, he was the most remarkably stoic person. He never complained … certainly not that we were ever aware of it. He just put up with it, he got along with it. And I think that Gordonstoun probably put a little bit of steel in his backbone."

The documentary shared that Charles defended the school during his House of Lords speech in the mid-‘70s.

"I am always astonished by the amount of rot talked about Gordonstoun and the careless use of ancient clichés used to describe it," said Charles at the time. "It was only tough in the sense that it demanded more of you as an individual than most other schools did — mentally or physically."

"I am lucky in that I believe it taught me a great deal about myself and my own abilities and disabilities," Charles shared. "It taught me to accept challenges and take the initiative."

Charles became king when his mother, Britain’s longest-reigning monarch, passed away on Sept. 8. She was 96.