Once upon a time, many years ago, there was a beautiful young woman who had a dream for her son of the kind shared by millions of mothers all over the world, which was that he could be - and indeed must be - whatever he wanted to be in life. The only trouble with this charming notion was that it made the boy's father quite angry. And it did so for the simple reason that, barring tragedy, revolution or a personal decision of historic proportions, the child could not actually be what he wanted to be at all. For his name was Prince William and he was destined to be king.
But looked at through the prism of where we are today, few would argue that Princess Diana was wrong to have put such ideas into the head of her 11-year-old son. I hope it is many decades until anyone gets around to discussing what will be marked on William's gravestone, but we could already have a stab at it: He did it his way.
Yes, he may be king one day. But within the confines of that straightjacket, William does seem more than usually determined to carry off his destiny in a manner of his choosing. Indeed, the quickest way to make him really, really mad is to suggest that something should be done in a certain style because it has always been done that way.
He fights protocol tooth and nail. He doesn't like titles, nor care much for pomp and circumstance. He prefers most things in life to be kept low key and simple.
So you can imagine that negotiating details of the wedding with the keepers of the traditional flame across the park at Buck House has not been without its issues. It is no great secret that William would much rather be getting married in the village church in Bucklebury with 200 of his closest mates. He accepts the fact that Westminster Abbey will be full of dignitaries he has never met and that hundreds of millions, if not billions, of people will watch the event on TV all over the world, but he doesn't particularly relish it. I mean, would you?
He has seen the way this life has constrained his father and - literally - destroyed his mother and he views it with caution and suspicion. He is at his most decisive and impressive when his protective instincts are aroused, particularly on behalf of his bride and her family. Indeed, what he would really like as soon as he and Kate are married is to return to Anglesey and hole up there for as long as possible in pursuit of a conventional military career and domestic happiness.
But here is the conundrum: if William remains in some ways cautious of the life fate has allotted him, he does seem to be driven by a desire to perform the role with gusto. As soon as the earthquake hit New Zealand's South Island in February, for example, he was chomping at the bit to get out there and pay his respects. And he didn't stop hassling until he landed in Christchurch a few weeks ago.
He understands the importance of leadership. He was proud of his role in the World Cup bid, even if he was perplexed by the result. He appreciates how privileged his existence is. He understands the importance of doing his duty and wants to be a good king. It is clear to anyone who knows him that his life has long been characterized by an aching determination to make sure he never gets anything wrong, an ambition which is notably shared by his wife-to-be.
I used to look on perplexed as Kate was painted in some quarters as a grasping and lazy social climber with her eye on the main chance, because what I have seen is a loyal and rather straightforward woman who has been determined throughout to avoid doing anything that would make her boyfriend's position more difficult.
William will turn 30 next year and about the worst thing you can say about either of them is that he once landed a Chinook in her parents' back garden. He's got the wrong side of a bottle of whisky a few times, it's true, but that's about it.
Nobody is suggesting they are perfect, but they have kept a remarkably clean sheet. For a couple destined one day to assume such an elevated position of national leadership, it's a record that is hard to argue with.