In the topic for S03.E09, Milburn Stone wrote,
Charles's most sympathethic biographers acknowledge that until the last two decades, his greatest character fault has been an obdurant self-pity, and his greatest occupational weakness has been a need for validation from others. Sometimes this insecurity has been blamed on his introspective nature or his willingness to deliberate: I disagree that either quality is at fault, or a fault. Even in a Prince of Wales.
But some are born with an innate ability to go it alone, as well as a drive to measure themselves against standards they select and re-shape with their bare hands. (See Anne the No-Nonsense, the peerless Princess Royal with nerves of steel.) It is a confidence that not only knows, "You'll do as I say" but conveys via viscera, "You'll do as I say, and all will be well." You see it among children in pre-school and on the playground; you see it among dogs set free in the dog park. It's animal magnetism: what we in the West, anyway, call leadership, and in its presence fellow creatures great and small feel safe.
Charles wasn't born with this, and worse luck, his nature's need to be valued and nurtured was met by...well, his parents, and their natures: never more alike than in how much they differ from their son. With either his mother the Queen or his father The Prince, Charles would be forever be barking up the wrong tree. What they failed to see was that Charles didn't need toughening up as much as he needed jollying up and bolstering up. Real reassurance from a benevolent alpha would, Charles rightly sensed, enable him to thrive. That's what drove him, as a young man, from mentor to mentor.
But the mentors he chose (or who chose him -- first Mountbatten, then Laurens van der Post) were no Socrates to Alexander, or even Falstaff to Prince Hal. They weren't men that the young Prince might go to school upon and then surpass, without a backward glance. Or they might have been, but only for another prince, at a much younger age. Charles needed his mentors to appreciate him as much as to educate him, and that gave them the means and the license to use him. It's as Morgan has his Anne say: "We (meaning you, Charles) need to be sure that we're using them, and not the other way around."
I think Charles still found value in what Mountbatten and van der Post offered, simply because, despite all, they were fond of him, they saw him and they listened. To paraphrase Charles Ryder in Bridehead Revisited: "They were the forerunners." And he seems to have found the strength to be at ease in his own skin, now that he can look back on the first three-score-and-ten years of his life and see that the crown was never to be its culmination. What he was really waiting for, was for something within -- slowly cultivated through a fulfilling marriage and conscientious daily life -- to take root and grow. Not majesty, but maturity. Not rule, but peace.