Charles Spencer is opening up about Queen Elizabeth’s posthumous offer to Princess Diana.

The Daily Mail published a new excerpt of the 9th Earl Spencer’s upcoming memoir, Swan Song: Diana, My Sister, on Friday, Sept. 18, which offers new details of the days following Diana’s death on Aug. 31, 1997.

The new passage includes Spencer’s account of the powerful eulogy that he delivered at his sister’s funeral — in which he described Diana as “the most hunted woman of the modern age” — as well as the offer he says the Queen made to his family following the service.

Spencer recounted being on the Royal Train back to Althorp, his family home, when he was approached by Robert Fellowes, the Queen’s Private Secretary.

“When we had gone some miles, Robert beckoned me to follow him into a quiet corner of the carriage,” Spencer wrote. “ ‘I have just received a call from Her Majesty,’ he said, in the grave tone that he always adopted when talking about the Queen, ‘and she would like to offer Diana her HRH title back.’ ”

Following her marriage to Prince Charles in 1981, Diana became Her Royal Highness (HRH) The Princess of Wales. She was also given the titles of Duchess of Cornwall, Countess of Chester, Duchess of Rothesay, Countess of Carrick, Baroness of Renfrew and Lady of the Isles.

However, following her divorce in 1996, Diana was stripped of her HRH styling and became Diana, Princess of Wales.

Spencer wrote that he thought about what his late sister would have wanted.

“She had been dreadfully hurt by the removal of that title as she exited her marriage,” he recounted. “It had seemed so petty and vindictive. While she was no longer to be married to one future king, she would always be mother to another.”

“After a moment, I felt that I knew in my bones how she would view this posthumous award: ‘That’s very kind of the Queen, of course. But what’s the point, Robert? Now? I mean — Diana’s dead.’ He nodded and looked down, then said: ‘I thought you might say that.’ ”

Spencer admitted that he’s wondered if he made the right decision in rejecting the Queen’s offer. “Maybe Diana would have seen some point in having HRH carved on her tombstone. More importantly, perhaps her sons would have valued this gesture from their paternal grandmother to their mother?”

“But I felt especially protective of Diana in that moment and had no doubt that the consolation prize was hollow, however well-meaning the Queen’s gesture,” he said. “The title should never have been removed during her life, in which case it would not have been necessary to offer it to her in death.”

The debate over HRH styling has come up more recently pertaining to Diana’s younger son. Following Prince Harry and Meghan Markle’s 2020 decision to step back as working royals, they retained their titles of Duke and Duchess of Sussex. They also formally retained their HRH styling but would no longer “actively use” it.

Amid Harry and Meghan’s recent return to the U.K., a letter was issued via the Lord Chamberlain, Lord Benyon, on Sept. 7, in which the King iterated the couple’s status as non-working members of the royal family.

“It follows that there is no change to the current status of the Duke and Duchess of Sussex,” the letter stated. “Their styles as His and Her Royal Highness remain in abeyance and are not used.”

However, a source close to the Duke and Duchess of Sussex pushed back on the description of the couple as “private citizens,” telling PEOPLE, “They are public figures. Members of the public know who they are. The idea that they can live a normal, ‘private’ life is sadly not realistic.”

Other excerpts from Swan Song have been released ahead of the book’s publication next week. In one, Spencer claims that, in a phone call with then-Prince Charles shortly after Diana’s death, his former brother-in-law “unleashed what I have always taken to be his pent-up contempt for Diana,” telling him, “We’ll forget her soon enough!”

King Charles and Buckingham Palace released a rare statement in response to that account, which said, “While we do not comment on books as a matter of principle, His Majesty is mindful that the pain of fraternal grief can cloud reason, affect judgment and color memory in ways others do not recognize, even many years after such a loss.”

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Swan Song: Diana, My Sister was announced last month. The book marks the first time that Spencer speaks “openly” and “at length” about his late sister, and he said he was inspired to write it after being “inundated” with requests for interviews as the 30th anniversary of Diana’s death approaches.

“The aim of this book is to tell the truth about Diana from her brother’s perspective, just as I attempted to do when speaking at her funeral,” Spencer said in a press release. “As with my eulogy, I want to speak on Diana’s behalf and do so in an openly positive way.”

After recording the audiobook, Spencer recounted the experience in an Instagram media post, calling Swan Song the “most personal” book he’s ever written.

“At heart, this is a brother’s simple tribute to an extraordinary sister,” he wrote. “When I finished the recording, I thought: ‘That is exactly what I wanted and needed to say — and she would, I reckon, have approved of every word.’ ”