It was the Leonard Cohen bit that did it. There were William and Harry, all ready to "fess up" - as the young people say, I hear - to Ant and Dec about their favourite rap acts when - doh! - Dad blunders in to tell all about the famously morose Canadian singer-songwriter, a "chap" he thinks is "terrific", and asks his sons if they have heard of him. Strangely enough, they haven't.
For years, Charles has been the overgrown boy prince everyone thought was weird. Now, he's someone we can all relate to - he's come out as an Embarrassing Dad (ED).
It was a model ED performance. Displaying tastes in music that make your offspring think you're sad is one of the classic ingredients. Another is your choice of clothes. True, the younger princes weren't exactly à la mode, their open-shirt collars folded stiffly over the necks of hearty sweaters, as if policing the boundaries of the casual. But, like, Dad? Like, hello? Like, that double-breasted jacket? Like, that... tie?
But listen up, your Royal Highness: we've all been there. I'll probably be going there today. Should the weather turn out sunny, I'll be embarrassing my daughter by being down the park with her wearing that hat of mine which, to me, is just a garment for stopping my pate turning red but to her has the potential for demolishing her cred with any friend of hers we see. "I need the hat," I'll protest, though she won't hear me. She'll already have fallen 50 yards back to shelter behind her less embarrassing mum.
I know this because it happened the last time, which also happened to be the first clear-cut ED episode with the child in question, who happens to be a mere 10 years old. Becoming an ED is one of father- hood's most galling milestones. I've been past it three times already and the sobering impact doesn't really fade. To some extent it just provides the latest unwelcome reminder that you're ageing. The greater part, though, is what it tells you about your kids. Throughout the first half of their childhood they loved your being silly: the mucking about, the jokes, the rich stupidity. Then puberty informs them that these endearing qualities are, in fact, your most mortifying, and makes their little toenails curl with shame.
Yes, they are growing up and you, Dad, are in a whole different ball game. It is a game that requires you keep your distance at the time in their lives when you may feel they need your guidance most. It isn't just a dad thing, either. It happens, in different and differing ways, to mothers too. Might even Diana's sons in adolescence have pretended not to see her had they passed her on High Street Ken with their pals?
There isn't much EDs can do but grin and bear it: being dads, we are embarrassing almost by definition, anyway. Maybe, though, we can seek some consolation. When my eldest, now 21, was in her mid-teens she dreaded my attending parents' evenings at school with her because our facial resemblance was so strong. "I'm her dad," I'd tell her teachers. "I can see that," they'd beam, knowingly. At the time I loved it and she loathed it. Yet it's become the stuff of fond nostalgia now.
Then there's my oldest boy, aged 16. Now he is emerging into the light. Every second Tuesday, he joins me and some fellow old codgers to play football. When he first came I stopped bantering with the others, because sometimes even to speak in your teenager's presence is to be an excruciating ED. But then he scored a goal or two and made some tackles. He even smiles now when I make myself look a fool. For me, this is immensely reassuring. It tells me that he's growing up completely normally and that, should he become a dad one day, he'll be an embarrassing one too. And that's cool.