Everyone has heard of Balmoral, the Royal family's majestic 50,000 acre Scottish estate and the setting their annual pilgrimage to the Highlands. But what many people don't know is that there's another royal retreat hidden deep in those forests, just six miles from the castle, a secret sanctuary King Charles has managed to keep just for himself.

It has been the scene of many pivotal moment's in the King's life. It is here he would hide out with his beloved Grandmother, the Queen Mother, when it all got too much at his hated Scottish boarding school Gordonstoun.

It is where he enjoyed family holidays with Princess Diana in the early years of their marriage when William and Harry were little.

It was where he chose to recuperate from a serious polo accident and where the scandal of his affair with Camilla Parker Bowles was blown wide open when she was spotted by a photographer leaving the secret hideaway house while Diana was 500 miles away in Kensington Palace. Later it would be where he would propose to his beloved Camilla and where they had their honeymoon after their marriage in 2005. It is in fact the only royal property that could be truly considered a marital home to them.

When his mother Queen Elizabeth died in 2022, it was here, not Balmoral with the rest of the royals, that he and William slipped off to, to discuss the funeral and the future. In fact it was here Charles had been, taking a break from his dying mother's bedside, when the call came through to tell him that she had passed. "Your Majesty" a courtier began, and it was all Charles needed to hear to know that he was now king.

Learning the most important news of his life happened here, his favourite place in the world. For this is Birkhall, the house that means the most to King Charles out of his huge property portfolio. Now a new TV documentary explores its' place in recent royal history and begs the question, can the monarch, amidst an ongoing national cost of living crisis and under pressure to keep cutting costs, keep hold of his beloved bolthole?

Ingrid Seward, editor-in-chief of Majesty magazine tells the programme :"It is the property that means the most to him. It is completely secluded away from everybody. It is very hidden, very private."

Former BBC royal correspondent Jennie Bond adds: "I think when he arrives at Birkhall it is a case of 'phew, we are here.' They have a sense of freedom there they don't have in their own lives."
Indeed it is easy to imagine the King and Queen curled up on a chintzy sofa, a whisky in hand, in front of a roaring fire. For them it is a romantic retreat and Birkhall's history is steeped in royal romance.

Queen Elizabeth and Prince Philip had their honeymoon there as did the Duke and Duchess of Kent and Prince Edward and Sophie, Duchess of Wessex.

But what is it like inside? The public did catch tantalising glimpses of the interior for the first time during the pandemic. The couple isolated there when Charles caught Covid early in 2020 and later as he carried out engagements via zoom we got to see into his clutter filled office, laden with books and family photos everywhere. Camilla's zoom room by contrast was light, airy and flower filled.

However this new documentary reveals much more. Jennie Bond describes is as "cosy but elegant." Set over three floors, it is small for a royal residence. Chandrika Kaul, a Professor of Modern History at the University of St Andrews, whose research interests include the British Monarchy in Scotland, adds: "The interiors are graceful and elegant with a touch of comfortable of country house thrown in but it is the gorgeous grounds that are closest to Charles' heart."

Jennie agrees adding: "The gardens at Birkhall are stunning and Charles has put his own mark on them very clearly."
The immaculate lawn slopes down to the bell garden, a beautifully planted flower and vegetable garden in the shape of a bell with little pathways running through.

Daily Express gardening columnist and author of "Royal Gardens of the World" Mark Lane reveals how Charles has planted little strawberry plants along them for the visiting grandchildren to pick and enjoy. He says their funny loving grandfather even installed a bouncy bridge for George, Charlotte and Louis on which he insists to them "you must bounce, you must bounce."

However it is the 1935 Wendy House, complete with thatched heather roof and bark walls that the late Queen Elizabeth and her younger sister Princess Margaret used to play in that they run to first.

Always keen to inject some fun into the beloved garden and ever the organic gardener, the King also brought in eight runner ducks to eat the slugs and other garden pests. Like Highgrove there are no pesticides here.

There are red squirrels though and Prince William revealed his father has named them all and can tell them apart by their individual characteristics. He even lets them come into the property and jump around the dining room.
Then are no less than eight Grandfather clocks and carriage clocks in that dining room.

When Birkhall belonged to the Queen Mother none of the clocks were set to the correct time and she would take great delight in the constant chimes going off at different times interrupting conversations.

One of the first things Charles did when she left him Birkhall following her death in 2002 at the age of 101, was to have all the clocks set to the correct time so although there is still loud ticking and chiming, it is at least altogether. Her barometer remains hanging in the hallway and her coat on a peg.

Jennie Bond said: "The loss of his grandmother was devastating. She gave Birkhall to her favourite grandson but it was in a 1950s time warp so he set about renovating it. He and Camilla refurbished it together with antique furniture and rugs from the Middle East."

Birkhall had of course been refurbished before by previous royals.The little Scottish lodge, built in 1715 by Captain Charles Gordon and his wife Rachel out of local stone, was acquired by Prince Albert, consort to Queen Victoria, as part of the Balmoral Castle estate in 1849.

It given to their eldest son, Albert Edward, Prince of Wales, who only spent one night there before declaring it was too small, preferring the larger Abergeldie Castle. Queen Victoria had the grand front porch added so she could get into her carriage without getting wet.

Years later the Queen Mother would travel there her by limousine from the airport, with her entourage of 20 servants following behind in a rented coach. Always keen on parties she added four new bedrooms with en-suite bathrooms to accommodate more guests but forgot to have downstairs loo installed. So one was fitted under the staircase and the flower filled smallest room was officially opened by the Queen Mother who flushed the chain and announced: "I now declare Arthur's seat is open." Sir Arthur Penn served as Treasurer to the Queen Mother and had overseen the works. It was also a reference to the Scottish hill in Edinburgh of course.

Birkhall in those days was rather chintzy and full of tartan and whimsy, crammed with ornaments, and decorated rather like her London home Clarence House. Now able to accommodate more guests the programme reveals how one particular guest was banished from Birkhall forever after a major social faux pas.

Ingrid Seward said: "There was a lot of drinking and lot of party games." One game was 'racing demon', an extremely competitive game. Jennie Bond added: "The Queen Mother liked to win and most guests understood the unwritten rule that the Queen Mother had to win."

However one guest, Lord Atholl was convinced he had won, which he had, and demanded a recount. He was never invited ack to Birkhall again.

For Charles, Birkhall is a constant reminder of his "beloved granny." Jennie Bond said: "For Charles she was this haven of security and affection, laughter and love and whenever he could he would make the two hour journey from Gordonstoun to see her at Birkhall. It is where they formed their very strong bond."

Still seeking that haven to this day Mark Lane adds: "He likes the idea that even if the rest of the family are at Balmoral he can still escape and have a wonderful space of his own for him and Camilla." But how long he will be able to keep his luxurious love-nest isn't clear.

While on paper he is Europe's richest monarch, worth £1.8 billion, in reality, much of his wealth belongs to the Crown.
The Royal Family's annual outgoings for 2023/2024 were £90 million with more than two thirds of that going on maintaining the houses and the 1000 plus staff needed to run them.
Jennie Bond concludes: "He is aware the monarchy has to be accountable so I don't know what is going to happen to Birkhall.

"King Charles has so many properties. I don't think it is a good look and I think William might feel the same."
However Ken Wharfe, former royal protection officer to Princess Diana, disagrees adding: "The house is littered with royal history and that and the King's current connection to it, is enough reason for it to remain part of royal life"

Royal Historian Wesley Kerr agrees adding:"I think Birkhall will long be associated with the House of Windsor for years to come."

* Birkhall: A Private Royal Residence, Channel 5, tonight (Saturday 21 June), 7.30pm.