‘I had a dream,’ he once recalled, ‘that I was going to escape and hide in the forest, in a place where no one could find me, so I wouldn’t have to go back to school.’ A housemaster of that time described the school thus: ‘Good for the very clever, good for the laird’s idiot son, but not so good for the average boy.’ And in matters academic and athletic, Charles was never other than average. He only managed to pass O level mathematics at the third attempt. His history was something of a struggle (on one well-reported occasion his tutor, Robin Birley, shouted at him in front of the whole class, ‘Come on, Charles, you can do better than this – after all, this is the history of your family we’re dealing with!’). He was disappointing at rugby and cricket.

Where he did excel was in music and acting. He was taught to play the cello by an old German woman who had been at the school since Philip’s day. And his ability on the stage was quickly noted by Dr Eric Anderson, who would go on to become headmaster of Eton. Anderson cast him in the role of Macbeth and he turned in a memorable performance. However, Prince Charles sees it in an altogether different light and still talks about the humiliating day his parents came to the school to see him perform and his father burst out laughing.

‘I had to lie on a huge fur rug and have a nightmare,’ Prince Charles remembers. ‘My parents came and watched along with other parents. I lay there and thrashed about and all I could hear was my father and ha ha ha. I went to him afterwards and said, “Why did you laugh?” and he said “It sounds like the Goons.” ’

In 1994, Charles revealed to his official biographer, Jonathan Dimbleby, that he felt ‘emotionally estranged’ from his parents and all his life he had yearned for a different kind of affection that they had been ‘unable or unwilling to offer’. His revelations hurt his parents, but all Prince Philip would say on the record is that they did their best. And according to Lady Kennard, their best wasn’t so bad. She maintained Philip was a ‘wonderful parent. He played with his children, he read them stories, he took them fishing, he was very involved.’

The Queen Mother, aware of her grandson’s introverted nature, had argued that he would be better served at Eton College, on the other side of the Thames from Windsor Castle, and with 600 years’ experience of accommodating the wide interests of its pupils. A number of the Queen’s advisers agreed with her, but Philip was not to be swayed and Gordonstoun it was. ‘In effect the decision meant an attempt to mould him in his father’s image, to which . . . he did not naturally approximate,’ royal expert Dermot Morrah wrote.