Queen Elizabeth II attends an Armed Forces Act of Loyalty Parade in the gardens of the Palace of Holyroodhouse

Queen Elizabethwas aware that the clock was ticking during her final year, royal biographer Robert Hardman writes in his new book onKing Charles.

Queen Elizabeth died on Sept. 8, 2022, at age 96 during the 70th year of her record-breaking reign, and Hardman sheds new light on details around her death inThe Making of a King: King Charles III and the Modern Monarchy(out Jan. 18).

In an excerpt of his book in theDaily Mailon Saturday, Hardman writes that the Queen’s exact cause of death is unclear because she had been “suffering from multiple conditions in her final year.” (Biographer Gyles Brandrethpreviously reportedthat the Queen had myeloma, a bone marrow cancer and that the palace refused to comment.)

“‘She had come to realize that the medical prognosis meant she was not going to emulate her mother and reach one hundred [theQueen Motherdied at age 101 in 2002], so she had been determined to make the most of that year,’ ” Hardman quotes a friend as saying inThe Making of The King. “‘She made sure she had all the family over the summer, so that the young ones in particular would always be left with happy memories of her.’ ”

Queen Elizabeth on the the balcony of Buckingham Palace during the Trooping the Colour parade in June 2022.Jonathan Brady - WPA Pool/Getty Images

Queen Elizabeth II watches from the balcony of Buckingham Palace during the Trooping the Colour parade

Jonathan Brady - WPA Pool/Getty Images

Due to the Queen’s advanced age, serious thought had been given to the possibility of a regency, which would allow Charles to stand in for her if she was deemed physically or mentally unable.

‘With the Queen Mother going on past her 100th birthday, of course we had to think that the Queen would reach the same age. A regency seemed almost inevitable. That would have been very difficult,’ says a senior former aide, according to the excerpt.

However, Charles was reluctant to discuss the matter at length.

‘You could turn up with all the papers and he would say, ‘Have you been through it all? Are you happy with this?’ and that would be that,’ an aide says inDaily Mail’s excerpt. ‘He didn’t want to dwell on the details… I think he felt that if you reach out for something, you are tempting fate.’

The Queen Mother and Prince Charles in August 2000.UK Press/Getty

Prince Charles sits next to the Queen Mother as she waves to admirers on the occassion of her 100th birthday celebration August 4, 2000 in London. Buckingham Palace announced March 30, 2002 that the Queen Mother has died

UK Press/Getty

Queen Elizabeth also spoke to her family about where she might spend her final days, Hardman says.

“Right to the end, she was endearingly conscious of causing unnecessary inconvenience to others,” he writes, according to the excerpt.

“There was a moment when she felt that it would be more difficult if she died at Balmoral,” the Princess Royal said in the special, which premiered on Boxing Day (the day after Christmas) in the U.K. “I think we did try and persuade her that shouldn’t be part of the decision-making process. So I hope she felt that that was right in the end,” Princess Anne said.

The Making of a King: King Charles III and the Modern Monarchy

Pegasus Books

Sources told PEOPLE at the time of the late Queen’s death that it had been fitting that she spend her last hours at Balmoral because it was such a special place for her and her family.

“Today would have been Her Late MajestyQueen Elizabeth’s 97th birthday,” the caption read. “This photograph — showing her with some of her grandchildren and great-grandchildren — was taken at Balmoral last summer.”

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ZaraandMike Tindall’s three kids Mia, 9, Lena, 5, and Lucas, 2, also smiled for the shot, as didPeter Phillips’ daughters Savannah, 13, and Isla, 11. The Queen’s two youngest grandchildrenLady Louise Windsor, 20, andJames, Earl of Wessex, 16, the children ofPrince EdwardandSophie, the Duchess of Edinburgh, stood behind their younger cousins.

source: people.com