Melanie McDonagh: That's quite enough from you, young man

Perhaps the nearest he got to dangerous controversy was where he insisted he intended to keep his "child streak" (er, would that be nightclubs or fights?): "I've got friends of mine saying, before I went into Sandhurst, 'Don't change, don't change.' Well, I'm not going to. I'd prefer to stay the same, if that's all right with everybody." Of course, what he's actually saying is that he doesn't actually care what we think. Nor - within limits - should he.

What people don't seem to understand about the Royal Family is that they're not required to have interesting views. The one member of it who is incessantly controversial is, of course, Prince Charles, and it has not necessarily advanced him in public esteem. The Queen addresses the nation every Christmas, but her sentiments are sufficiently opaque to give almost nothing away about her actual opinions. And precisely because she keeps her trap shut, her mystique is undiminished, and the regard in which she is held is a phenomenon. We know perfectly well that she is a committed Christian of unremarkable Protestant stamp, with an overriding interest in horses. But she keeps her enthusiasms to herself: the less she speaks, the more she hears and the more she is regarded as a repository of the wisdom of the nation.

There is little as attractive as the capacity of a public figure to say nothing at all. I grew up in Ireland in a republic whose presidents, prior to the tiresome Mary Robinson, were men of impeccable dullness held in universal esteem. They did their job and we respected them for it. At its most effective, the monarchy works the same way - for the hereditary principle invests the person of the monarch with sufficient gravitas for its holder to need to do almost nothing at all except keep out of trouble.

If Prince Harry continues with his Army career, preferably serving with distinction in some foreign conflict, stays out of really louche company, is polite to photographers and behaves agreeably at charity events, he will do very well. What he needs to avoid like the devil is any Dimbleby figure telling him that the nation requires to hear him put his case.

And he is not the only one who should avoid any but the most anodyne remarks. Just see what happened to the brilliant, beautiful Zadie Smith, whose disobliging comments about Britain to the New York magazine were, she says, quoted drastically out of context. It's just unfortunate that she gave the interview at all, or indeed spoke about anything except literature, on which she is as insightful as you might expect. If we were left simply to read her novels and admire her beauty, her image would be almost flawless.

Of course, we like it when public figures make asses of themselves and put their views in the forum for the rest of us to dispute with and criticise. But if they want to preserve their appeal, they shouldn't pander to journalists. They should keep their views to themselves, and we'll love them all the better for it.