Prince Harry left the world utterly surprised with his announcement of an upcoming memoir on his life on Monday, and the royal family did not have any clue about it either.

According to a report in Mail Online, the Duke of Sussex did not even warn his father Prince Charles about his plans to write the explosive memoir, which will give sensational details on the inner workings of the royal family. The 36-year-old is due to submit the first manuscript of the memoir in October, and it is expected to be released late next year, the platinum jubilee year of the reign of his grandmother Queen Elizabeth II.

Experts have told the outlet that the Duke will have been given "at least" a $20million (£14.6million) advance for the memoir, with millions more to be made in sales. The royal has said he is "excited for people to read a firsthand account" of his life that's "accurate and wholly truthful," but the same can't be said about his father and other senior royals who are still dealing with the consequences of his tell-all interview with Oprah Winfrey.

Sources close to the Prince of Wales said that he was "surprised" at the memoir's announcement, and that the royals had not been warned in advance that a book was in the offing until the news broke on Monday. One royal insider sarcastically called the memoir, "A book by Harry, as written by Meghan."

Another source revealed that the announcement had provoked "much eye-rolling" at Buckingham Palace. "I think everyone is just tired of being angry when it comes to those two (Harry and Meghan)," the source said.

"They have spent the last 18 months doing everything they promised Her Majesty they wouldn't do – making a living off their previous lives and status as members of the Royal Family. It's depressingly predictable, unfortunately," they added.

Harry's statement, about the book that he would be writing about his "mistakes" and the "lessons" he learned, has also raised some eyebrows. Royal sources instead said that the Duke had "never been one to willingly admit" any mistakes and had spent the last three years "blaming everyone except himself and his wife" for their fallout with senior members of the royal family.

In addition, "The Morning Show" on Channel 7 pointed out that Harry signed off his statement with his royal title "Duke of Sussex" despite starting the message by saying that he is "writing this book not as the Prince he was born but as the man he has become." "Talk about having it both ways!" entertainment reporter Peter Ford said on Tuesday, drawing laughs from hosts Larry Emdur and Kylie Gillies.

Meanwhile, royal expert Robert Jobson told FEMAIL that the book will only fuel the tension between the Sussexes and the rest of the royal family, and will be "hugely damaging to the House of Windsor and Monarchy as an institution."

"As night follows day, this was always going to happen. It will become an international bestseller, but at what cost to the monarchy? There will be nowhere to hide," Jobson said.

British Royal Family
British Royal Family Photo: AFP / Tolga AKMEN