Hidden away at the heart of Prince Charles's 15-acre Highgrove estate is a strange little building. Part Provencal retreat, part stone fortress, it is simply named The Sanctuary.

Based on a design of four semi-circles attached to a cube, sacred geometric principles of building, it has carved above its entrance a plea: "leighten our darkness we beseech thee O Lord."

To enter this blessed sanctum, HRH turns four wooden knobs in ritual sequences. Here in this dark space, lit only by candles and the flames of an open fire, this king-in-waiting may never be disturbed or intruded upon as he ponders the vagaries of his life, or, more pretentiously, seeks divine inspiration.

Edgily semi-aware no doubt, that he was in danger of attracting yet more ridicule, Charles kept the cameras a discreet distance away from the building during the filming of this week's 90-minute BBC documentary into his life on the eve of his 60th birthday.

For in a world sharply divided as to the merits or demerits of this ageing heir to the throne, the small refuge could be perceived either as a true statement of his spiritual quest for meaning, or the self-indulgent whimsy of a pampered prince. Perhaps it unwittingly also showed the paradox of a prince in the 21st century.

At heart a true medieval monarch: quick to anger, to put aside wife or wives, to cut to the chase of his obsessions, to have his way regardless of all obstacles, and to question those who question him.

One, who, like his ancestors, then repairs to his private chapel to shrive himself for his sins of indulgence, wrath, and arrogance.

Or, on the surface, the original middle-class, middle-aged Grumpy Old Man: one who could slip easily into the TV series, bemoaning the youth, the culture, the vulgarity, the political correctness of modern life, as he has done in numerous speeches and letters; a mirror image of a generation forged in Harold Wilson's socialist vision through a new visible youth against a backstory of the Beatles, the Beach Boys, and in Charles's case, the Three Degrees.

A generation now aged 60 but still feeling young and somehow left out of all that is happening in the world. A generation who write notes to themselves and stick them in pockets, like Charles, because otherwise they would forget what they meant to do.

Running this theory past an intimate of Charles's yesterday, the response was cagey. "Well, that's a kind way of putting it," he said carefully. "And there is a lot of the King chosen by God' in Charles's mindset.

"At heart he frets and fidgets about his ultimate accession to the throne, but his belief in the natural order would never allow him to urge the Queen's abdication in his favour , whatever he may hope for in his heart.

"He is painfully aware of time passing ... of his time passing. It is the cause of his melancholia but, sadly, his over-riding weakness is vanity. He is a vain, vain man with little imagination.

"For all his talk of global warming, city regeneration, disaffected youth, he doesn't really quite grasp it. He doesn't live in the real world. If I ever told him that, he would be frightfully hurt, because he truly believes he understands real people. And of course, he would never see me again."

It is a cruel summing-up, and that from a friend. And it is true that he doesn't live in the real world. He still cannot understand how "the people" couldn't see through the manipulative myth created by Diana. Cannot accept his role in her downfall.

He was castigated when it was revealed that a valet squeezed his toothpaste on to his brush - it was forgotten that he had a broken arm at the time. Last week, a former cook revealed how he kept three pans of eggs boiling to have the perfect four-minute specimen ready for HRH's return for tea.

Wary from childhood of boys at school who would suck up to him because of who he was, sheltered by a protective nanny, Mabel Anderson; forged by a cynical grandmother in Elizabeth and a devious mentor in Mountbatten; he has few close friends, yet bizarrely surrounds himself by paid sycophantic aides.

Deeply insecure, he talks of "they" and "them" when suggesting his ideas will always be stalled for some deep reason. Who "they" are is never quite specified. The Establishment? The Press? You, Me? He would be equally horrified to learn that many members of Britain's aristocracy groan on hearing he would like to "come to visit and see their house or gardens".

"We dodge the timing," admitted one to me. "Of course it would be seen as an honour that he and Camilla were coming but, frankly, it's a nightmare. He expects our bedroom as obviously it will be the best in the house. So we all have to move rooms and then there's all his little peccadillos to attend to - the food, the security, the aides. He likes to hold court and he likes to meet new' people who care about all the things he does.

"The tragedy about Charles is that he thinks he's an easy guest. He really believes he's a modern royal."

It is easy to snipe at a future king who is trying to find his way in a bolshie, republican world. He has no precedent. Another close acquaintance said yesterday: "He's frankly knackered. He is constantly running all over the place, forming new charities, desperately convening meetings and trusts. He needs to stop and be content with what he has done. But I doubt he ever will. He's just too driven to prove himself. He's always wanting approval."

He should be content and proud of what he has done. In 1976, at the age of 27, he set up the Prince's Trust Fund with his Royal Navy severance pay and has changed the lives of thousands of inner-city youngsters.

He is responsible for more than 20 charities that raise £119m every year and support rain forests, traditional teaching, inner-city problems and raises awareness of everything from global warming to GM food crops.

His Duchy Organic brand makes more than £6m a year, helping youngsters who are unemployed, have been in care or prison or who are struggling in school.

He talks of his ability to organise conferences with the great and good as "convening power", but admits others call it "meddling". Yet when he hears the call of the republicans suggesting he gets a "real job", he is at a loss how to answer. Flawed, spoiled, slightly embittered and a touch self-pitying - like the rest of us - he can say only: "I've done my best."

Maybe it's time we allowed that he has.

The life and times of a monarch in waiting
PRINCE Charles was born on November 14, 1948, at Buckingham Palace. The eldest child of the then Princess Elizabeth and the Duke of Edinburgh, he was christened Charles Philip Arthur George on December 15, 1948.