King Charles' sweet frozen-in-time tribute to loved one who died decades ago

King Charles has a seriously sentimental side - and this heartbreaking tribute to a lost loved one proves just how deep it runs.

More than 20 years ago, Charles lost someone who had been incredibly important to him, and experts have revealed that to this day, he has kept a few key aspects of their belongings in his home in exactly the same place - as if they might walk back in the door any moment now.

The revelation came in the new Channel 5 documentary, Birkhall: The King’s Secret Sanctuary, which details the monarch's relationship with one of his absolutely favourite residences.

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Birkhall is positioned very near the Royal Family's famous Balmoral estate, where they gather every summer and spend weeks engaged in countryside pursuits like fishing and picnics, in the privacy afforded to them by the Scottish countryside.

The nearby Birkhall is a much more modest home compared to the grandeur of Balmoral, and since his childhood, it is said by the experts to have been one of Charles's favourite places to spend time - in part because of who it previously belonged to, his beloved grandmother, the Queen Mother.

"For Charles, she was this haven of security and affection, and laughter and love," explained former BBC royal correspondent Jennie Bond. The expert continued that during Charles's unhappy school years in the north of Scotland, his grandmother's home of Birkhall, and the warm relationship they shared, offered the young prince some welcome respite.

"When he was at Gordonstoun school in the north of Scotland, he would, whenever he could, take the two-hour journey to Birkhall to be with his beloved granny."

When the Queen Mother died in 2002 at her home of Royal Lodge, Windsor - at the ripe old age of 101 - the Scottish retreat of Birkhall went to Charles, who was left utterly bereft at the loss.

"For Charles, the loss of his grandmother was absolutely devastating," explained Jennie, but after taking over the property, he started undertaking essential refurbishments, updating the heating systems, and redecorating much of the place with the help of his now-wife Camilla.

However, Charles made sure that the Queen Mother's presence is still felt in the house, "Her coats are still hanging up, on the door...which is really sweet," revealed expert Afua Hagan.

This heartbreaking nod to his grandmother in his favourite home is not the only way he has paid tribute to the Queen Mother, the expert also revealed that he has kept the barometer she used to use to check the weather hanging up.

The Queen Mother was also a huge fan of clocks, the experts revealed, and used to have eight in the dining room alone - all set to "slightly different times" so they would chime out of sync with one another. The Queen Mother's guests were said to have been sent round the bend by this - but this reaction was something the quirky royal "thoroughly enjoyed".

Charles has kept her clocks hanging up, it is revealed in the documentary, "He kept all eight of those grandfather clocks in the dining room," Afua explained, "but he set them all to the same time, so it didn't drive everybody as bonkers as it had done before."

A royal author has previously claimed that the Queen Mother was actually "more of a mother" to her grandson than the late Queen Elizabeth herself - putting this down to the former monarch's gruelling schedule as head of state.

"In some ways, the Queen Mother was a mother figure to Charles just because the Queen became Queen when Charles was so young. There were a lot of tours of the Commonwealth and every time the Queen had to go away, Prince Charles stayed with the Queen Mother," Gareth Russell, who has written a biography of the Queen Mother explained to People magazine. "They had a great sense of humour, and she always encouraged him."

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