The British royal family is bracing themselves for another tell-all.

Omid Scobie has written an "explosive" follow-up to his 2020 book, "Finding Freedom," titled "Endgame." It promises to be "a penetrating investigation into the current state of the British monarchy – an unpopular king, a power-hungry heir to the throne, a queen willing to go to dangerous lengths to preserve her image, and a prince forced to start a new life after being betrayed by his own family."

The publisher noted that "Endgame" is based on conversations and interviews "with current and former palace staff, trusted friends of the royals and even family members themselves."

"The reality is that the royal family will see it as another bombshell book," True Royalty TV co-founder Nick Bullen told Fox News Digital.

PRINCE HARRY HAS ‘MORE TO TELL’ AFTER ‘SPARE,' MEGHAN MARKLE'S BOOK 'WILL ALMOST CERTAINLY BE UP NEXT': EXPERT

The British royal family standing together and smiling on the red carpet wearing glamorous outfits

The House of Windsor will be hit with a new bombshell book on Tuesday. (Max Mumby/Indigo/Getty Images)

Bullen is an award-winning documentarian who has been producing programs about the British royal family for 20 years. He has also worked closely with the king for about a decade. His streaming platform's newest documentary, "King Charles III - A Road to the Throne," examines the patriarch's reign, how it differs from the late queen and what the future of the Windsor family will look like.

King Charles in green suit adorned with medals and chains sits in a royal chair next to a crown

King Charles III is the subject of a new documentary on True Royalty TV. The special is titled "King Charles III - A Road to the Throne." (Alastair Grant)

"I think they’re tired," Bullen said about the publication of "Endgame." "I think … the anger has gone out of it. … A lot of the heat has gone out of it. It’s just a sense of, ‘Really? Again?’"

The British royals avoid looking at each other while in formal wear standing on the balcony of Buckingham Palace

The Duke and Duchess of Sussex (left, seen here with the Prince and Princess of Wales) stepped back as senior royals in 2020. They live in Montecito, California, with their son, Prince Archie, and daughter Princess Lilibet. (Max Mumby/Indigo/Getty Images)

Scobie is a royal watcher who some say serves as an unofficial spokesman for Meghan Markle.

In 2021, the Duchess of Sussex apologized for misleading a British court about the extent of her cooperation with Scobie and "Finding Freedom" co-author Carolyn Durand. At the time, the former American actress was embroiled in a court battle in London over a British newspaper’s publications of portions of a letter she wrote to her estranged father.

The duchess’ lawyers have previously denied that she and Prince Harry collaborated with the authors. But the couple’s former communications director, Jason Knauf, said in evidence to the court that he gave the writers information and discussed it with the Duke and Duchess of Sussex.

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Copies of Finding Freedom on top of a table

The 2020 book "Finding Freedom: Harry and Meghan and the Making of a Modern Royal Family" is a biography of Prince Harry and Meghan Markle, the Duke and Duchess of Sussex, written by Carolyn Durand and Omid Scobie and published by Harper Collins. (Chris Jackson/Getty Images)

"[It’s been said] that the Sussexes are trying to distance themselves from the [latest] book," Bullen shared. "I think that’s pretty tough for them to do because clearly there’s a lot of stuff in Omid Scobie’s book, ‘Endgame,’ that can only have come from sources very close to the Sussexes. And we know they had a relationship with him. … So, I think there’ll just be a great sense of ‘What a shame’ from the royal family. What a shame that this is happening again, just as things were beginning to calm down."

In January this year, Harry’s memoir, "Spare," was published. That book exposed deeply personal details about the prince and his relationship with the royal family, often in eyebrow-raising detail.

At the time of the book’s publication, Buckingham Palace officials declined to comment on any of the allegations. A spokesperson for King Charles didn’t immediately respond to Fox News Digital’s request for comment. A spokesperson for Kensington Palace, which represents William and Kate, told Fox News Digital they didn’t have a comment.

Copies of Prince Harrys memoir Spare on a top of a table

Prince Harry's memoir, "Spare," was published in January this year. (Justin Tallis/AFP)

Palace officials, as well as reps for the Duke and Duchess of Sussex, didn’t immediately respond to Fox News Digital’s request for comment about "Endgame." A palace rep previously told Fox News Digital they don’t comment on "such books."

Bullen revealed that in recent weeks it appeared hopeful that tensions would lessen between the royal family and the Sussexes.

"There was the call with the king for his 75th birthday," Bullen said. "We know that there was a phone call between Harry and the king. … Everything seemed to be going well. … People were trying to repair relationships. We heard that Princess Lilibet and Prince Archie had sent video messages singing ‘Happy Birthday’ to the king. It felt like there was some form of rebuilding. But here we are again with … another book … and more revelations. So, I think a tiredness would probably be the way it’s being felt in the household."

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King Charles in a red suit looking away as Meghan Markle in a pink dress looks up at Prince Harry who is wearing a uniform with medals

True Royalty TV co-founder Nick Bullen said the British royal family wants to move forward from "the Harry and Meghan circus." (Mark Cuthbert/UK Press)

It was long speculated that "Endgame" would reveal the identity of the royal who made comments about Prince Archie’s skin. During a televised sit-down with Oprah Winfrey in 2021, the duchess said the conversation took place while she was pregnant with her son. Harry later clarified through Winfrey that it was not his grandparents, Queen Elizabeth II and Prince Philip.

In an interview with "Good Morning America," Scobie said it was two royals who raised questions about Archie’s skin tone. However, U.K. laws prevent him from revealing their names.

Oprah interviews Prince Harry, Meghan Markle

Oprah Winfrey interviewed Prince Harry and Meghan Markle for a special in 2021 where they revealed their struggles with royal life. (Harpo Productions/Joe Pugliese via Getty Images)

"The names were mentioned in letters between Meghan and Charles that were exchanged sometime after the Oprah interview," Scobie explained. "We know from sources that Charles was horrified that that’s how Meghan felt. ... He wanted to, sort of as a representative of his family, have that conversation with her, and that’s why, I personally think, that they have been able to move forward with some kind of line of communication afterward, though they may not see eye to eye on it."

The British royals all looking somber in black attire in front of a car

The royal family last put on a united front with the Duke and Duchess of Sussex after the death of Queen Elizabeth II. England's longest-reigning monarch died in 2022 at age 96. (Kirsty O'Connor/Pool/AFP via Getty Images)

Ahead of the book’s publication on Tuesday, the New York Times published its review, warning readers that those "hoping for a final death blow of gossip will be disappointed." Regarding a chapter about Meghan and Harry, the Times wrote, "Their chapter reads like a press release cooked up by ChatGPT, and does little to shed light on them as humans."

Bullen said there’s "a real fear" within the palace of private conversations they have with the Duke and Duchess of Sussex. The couple stepped back in 2020 as senior royals. They cited what they saw as the media’s racist treatment of the duchess, 42, and a lack of support from the palace. The couple now live in California with their two young children.

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Prince Harry in a black suit with medals holding Meghan Markles hand, who is wearing a white coat dress and a matching hat

Nick Bullen said there is "a real fear" within the palace that private conversations with the Duke and Duchess of Sussex are being leaked. (Wiktor Szymanowicz/Anadolu Agency via Getty Images)

"I think the royal family just want to move forward from the whole Harry and Meghan circus," Bullen explained. "I think they want Harry back in the fold. They want relationships with the children and grandchildren. But there is a real fear – and I know this for a fact from people at a very senior level within the royal household – there is a real fear that the conversations with the Sussexes are not private and that they get leaked. And I think that’s the biggest fear that exists."

"It’s not that there’s unfinished business, it’s just that people are worried about discussing any business because it seems to find its way into books and papers and interviews," Bullen added.

Bullen alleged that the king, 75, is still hopeful to "rebuild" his relationship with Harry, 39.

King Charles smiling in front of his birthday cake

According to Nick Bullen, King Charles III received a phone call from Prince Harry on his birthday. (Chris Jackson/Getty Images)

"I think the king would like nothing more than to establish a relationship with Harry," said Bullen. "[Harry’s] his son. He loves him. Every father wants to have a strong and loving relationship with his son. So, I think the king is keen to make that happen. The king is probably very comfortable letting go … some of the things that have been said in the past to ensure he can have a relationship with him and his grandchildren. I think the king is trying to find a way of making it work."

"Whether that’s the case for the Prince of Wales or not is a whole other thing," Bullen added, referring to Prince William.

Scobie told People magazine that the relationship between the brothers is "beyond repair." Scobie said that William, who is heir to the throne, has prioritized his loyalty to the monarchy.

PRINCE HARRY'S FEUD WITH KING CHARLES, PRINCE WILLIAM AT INTERVENTION POINT: EXPERT

Prince Harry and Prince William with their backs facin each

The relationship between Prince Harry, left, and his older brother, Prince William, right, continues to be strained. (Dominic Lipinski/Pool/AFP)

In "Spare," Harry wrote that William once lashed out at him during a furious argument over the siblings’ deteriorating relationship. Harry said William labeled Markle "difficult," "rude" and "abrasive." Harry said William grabbed him by the collar and ripped his necklace before knocking him down. Harry said he had scrapes and bruises after landing on a dog bowl as a result of the tussle, for which William later apologized.

King Charles walking Meghan Markle down the aisle on her wedding day

Meghan Markle (seen here accompanied by her father-in-law, King Charles III) became the Duchess of Sussex when she married Prince Harry in 2018. (Owen Humphreys/AFP)

Numerous royal watchers have insisted that the relationship between the brothers has remained strained since the Duke and Duchess of Sussex made their exit.

Bullen alleged that William is still "very angry," especially following the publication of "Spare."

Prince William in a uniform walking behind his father in a matching uniform

According to Nick Bullen, Prince William, left, believes that Prince Harry behaved "very badly" to their father King Charles III, right. (Max Mumby/Indigo/Getty Images)

"I think the Prince of Wales feels that Harry has behaved badly and that he’s also behaved badly to his father," Bullen said. "I think the rebuilding of the relationship is coming from the king and that’s where it’ll start."

"I certainly haven’t heard of any huge makeup between those brothers," he shared. "I understand they have spoken. I don’t know when, but I think that the communication lines are open, but I think they’re limited."

With the publication of "Endgame," one thing is certain: The royals will continue to put duty first.

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King Charles III during his coronation ceremony at Westminster Abbey, London

King Charles III was crowned in May this year. Nick Bullen said the royals will continue to put duty first. (Victoria Jones/Pool via Reuters)

"Everything seemed to be going well until this book landed, which always seems to happen," said Bullen.

The Associated Press contributed to this report.