New light is being shed into how King Charles III reportedly leads his staff.

In Valentine Low’s "Courtiers: The Hidden Power Behind the Crown," insiders close to the monarch shared that Charles has a "fierce temper and a ferocious work ethic."

"Things would frustrate him, especially the media," an insider told Low, which The Times published from the book.

King Charles III

King Charles III was deemed "very demanding of himself" and expected the same from his staff, according to new book. (Jonathan Brady/Pool Photo via AP)

A former member of his household described him to go from "zero to 60 in a flash and then back down again." The insider shared that he "rarely directs" his anger to people.

A representative for Charles did not immediately respond to Fox News' request for comment.

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Other former members of his staff described the king as "never satisfied with himself or what he has achieved. People around him had to work hard to keep up." The insider added, "He had enormous stamina."

"He would drive people hard," according to "Courtiers: The Hidden Power Behind the Crown." "He was full of ideas, always asking people to go and do things. The workload as private secretary would be immense. He had strong opinions. He also had a proper temper on him, which was quite fun.

"He would rarely direct it at the individual. It would be about something, and he would lose his temper. He would throw something. He would go from zero to 60 in a flash and then back down again. Things would frustrate him, especially the media."

The book claims that Charles is "very demanding of himself" and expects the same from his staff. Phone calls reportedly come in "at any time," from after breakfast until 11 at night, even during Christmas, The Times shared.

King Charles III with Queen Elizabeth II on Buckingham Palace balcony at Platinum Jubilee

King Charles III took the throne after Queen Elizabeth II died on Sept. 8, 2022. (Chris Jackson)

"At any moment, he may want to call you about something. Working on his boxes, on his ideas, on his papers. The pace is pretty intense," an insider shared with Low.

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The monarch was described to be a "man on a mission" with a variety of different interests. The book shares how the king turned to different individuals with expertise in "architecture, alternative medicine, business, organic farming, housing, Jungian psychoanalysis, Islamic art, rainforests, crop circles and the media."

Low claimed that working for Charles meant dealing with the "helpful suggestions" from the advisers. He claimed that the king was "not always a good judge of who should have his ear."

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"Jimmy Savile, the broadcaster and charity fundraiser who, after his death, was revealed to have been a serial sexual abuser, wrote a handbook for Charles on how the royal family should deal with the media after big disasters," Low penned.

"Charles passed on his tips to the Duke of Edinburgh, who in turn showed them to the Queen," he claimed.

Prince Harry Meghan Markle Prince William Kate Middleton

Low is writing a second book, "Courtiers: Intrigue, Ambition, and the Power Players Behind the House of Windsor," which will shed insight on Meghan Markle, Prince Harry, Prince William and Kate Middleton. (Chris Jackson)

Charles took the throne after Queen Elizabeth II died at Balmoral Castle in Scotland on Sept. 8. She was 96. "Courtiers: The Hidden Power Behind the Crown" is expected to be released Oct. 6.

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In a second book, "Courtiers: Intrigue, Ambition, and the Power Players Behind the House of Windsor," Low will dive into the lives of Meghan Markle, Prince Harry, Prince William and Kate Middleton. This book is set to be released June 2023.