King Charles knew his mother had died after hearing two heartbreaking words

The death of the late Queen Elizabeth marked the end of an era. After 70 years on the throne, the UK said goodbye to one of its most popular public figures when she died at age 96 - and the new King had to mourn his mother, whilst also immediately stepping into the role he had spent a lifetime preparing for.

King Charles - then Prince of Wales - had been called to Balmoral on the morning of 8 September 2022, and told that it was a matter of time before his mother died. He and his sister - the ever-popular Anne, Princess Royal - took turns sitting by the former monarch's bedside, experts have revealed in a new documentary.

The new Channel 5 documentary, Birkhall: The King’s Secret Sanctuary, saw experts examine the heartbreaking moment that Charles became King. Charles had "been summoned to Balmoral" from his nearby residence of Birkhall, which the documentary reveals is one of his favourite places to spend time.

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The BBC's former royal correspondent, Jennie Bond, explained in the film, "He was told that it would probably be a few hours before she passed away." Royal expert and journalist Emily Andrews said, "Charles and Anne had been taking it in turns to sit with the Queen and then, I think, as she slipped into a coma, Charles needed a bit of fresh air and some nature.

"So he went to the grounds of Birkhall, and it was there that he took the call."

However, before the news had been officially delivered, the expert explained that Charles knew what had happened instantly, after hearing two words - ones that he had spent a lifetime preparing for, but that signified he had lost his mother.

"He knew what had happened," Jennie explained, "Because he was addressed by the person who rang him, the courtier, as 'Your Majesty' and then he knew, 'Well, my mother has died' and obviously he raced back to Balmoral to be at her side."

Despite the difficulty of their grief, Emily Andrews claimed that there was some relief for the Royal Family that the late Queen had spent her final days at Balmoral - her Highland estate, where she had spent many of the happiest times in her life.

"I think everybody in the Royal Family, actually, was really glad it happened in Scotland, and for Charles as well to be at Birkhall, where it's such a kind of safe space for him, he feels very calm and relaxed, I think was very important'.

Other members of the Royal Family made their way to Scotland to say their final personal goodbye to the Queen, including Prince William and Prince Harry - with the latter travelling up separately.

Devastatingly, Harry has revealed that he got the news his beloved grandmother had died through a breaking news notification - along with the rest of the country - after his plane was delayed getting to Scotland.

The Queen's coffin was then brought to Edinburgh, where it laid in rest, giving the public the opportunity to say goodbye. The coffin was then flown to RAF Northolt before being brought back to London where the lying in state in Westminster Hall took place before her funeral - with Princess Anne accompanying her mother every step of the way.

Anne, who was widely praised for her commitment to her mother and monarch during those days, was seen curtsying to the coffin as she met it at every stage - and called it an "honour and a privilege" to stay with her mother until the end.

"It has been an honour and a privilege to accompany her on her final journeys," Anne said at the time.

"Witnessing the love and respect shown by so many on these journeys has been both humbling and uplifting.

"We will all share unique memories. I offer my thanks to each and every one who share our sense of loss."

Birkhall: The King’s Secret Sanctuary , airs Saturday 21 June at 7.30pm on Channel 5.