"And there’s just one other thing, Dad. I’ve had my eyebrow pierced.” Children learn exactly when to drop the angry skunk into a conversation. It’s always over the phone, and they develop some sixth sense that gleans the precise moment when the lights change, when the third bell rings at the theatre, when the girl says, “The hygienist will see you now.” Ali had caught me in a particularly Trappist, Stygian restaurant. I was getting sideways looks from the maître d’ as I hissed into my cupped hand. “What? You what? How? Who? Where? Well, you can just go and unpierce it, young man. This is not a discussion. I’m telling you.” “Dad, chillax. I can’t unpierce it. You can’t unpierce a thing. It’s done. It’s cool. It’s fine.”

It isn’t fine. I’m not fine. You’re not fine. We’re not fine. Nothing in your personal or social meteorology is fine. I realised I was shouting in that “I’m not shouting” voice that men have when talking to women in high heels, children and labradors. All parents know that there are perennial, ulcerated family subjects that come round with the regularity of EastEnders plots: “I’m going to get a motorbike/a tarantula/a tattoo/be a chalet girl in Albania/vote Conservative.” Most of us know to avoid them, to defuse the rows with benign neglect. Real family crises aren’t these set-piece conflicts with their posturing and pouting, but the tyranny and terror of events, the stuff that falls out of a clear blue sky.

So I rather surprised myself at how badly I took the eyebrow piercing. It was such an obvious obstacle: such a well-marked pothole. But I stepped in it, and got properly angry. I’m still properly angry. What makes it worse is that I’ve got precious little commiseration from anyone else. His mother said, “I’m not mad keen on it, but we’ve got to choose where to have our arguments.” She’s saving her powder for his mock exams. Why can’t I have a row about both? Why can’t I get righteously furious about this and the exams? “You do what you like,” she said, “but you’re on your own.”

Most of my contemporaries laughed at me, generally without humour. One friend sighed with fraternal fatherly consolation and said he’d had much the same argument about a tongue piercing. His 15-year-old daughter had declared a desire to have a bar in her mouth. Why would you want that, he asked with commendable aplomb. “Because it’s sexy.” What do you mean by sexy? “Well, Dad, it’s all about oral sex.” And do you want every man who sees you smile to know you think so much about putting penises in your mouth that you had a sex aid stapled to your tongue? This is a conversation no father should have with his daughter. She thought twice about it. Not about putting penises in her mouth, but because of the photos of septic tongues on the internet.

The Blonde said I should stop being such an old git. But I am an old git — that’s what I bring to fatherhood. Oldness, and a certain knotty, polished, repetitive gittishness, kept between the bookends of fuddy and duddy. An eyebrow dumbbell doesn’t even have the excuse of being a sex aid: “See, what you do Dad, is head-butt them in the groin.” Unless you’re a Hindu bride, a face piercing is a sign of daft, dim naivety, and of gap-mouthed, asinine vanity. An utter inability to see yourself as others see you. And at 15, it has precisely and unequivocally the opposite message to the one you imagine: it makes you look juvenile, inexperienced and gullible. Journalists spend half their lives reading faces. We get good at it. I’ve yet to see how eloquence and profundity are improved by the addition of metallic exclamation marks. But what makes me most angry is the knowledge that some grown-up is making a living disfiguring the faces of 15-year-olds: a doubtless richly decorated and embellished matey bloke who looks like a credit to the Russian prison system.

“Well, at least he won’t be able to wear it at school,” another parent said to me. Well, actually, yes, he can. I particularly sent him to a school that doesn’t have those hands-out-of-your-pockets, do-up-your-morning-coat aspirations. So, quite understandably, they think a face-bolt is between him and me.

“I expect you can hear your father talking when you shout at him,” said the Blonde. Well, sometimes I can. But not this time. I know what my dad would have said: he’d have smiled and said, “I’ve seen people with plates in their lips big enough to carve a leg of lamb on. I once came across a tribe in the Moluccas that stuck sharpened bamboo into their perineums and inserted gravel in their foreskins.” My dad would have been very “chillaxed” about a piercing. He was more concerned with what elevated my brow than what was stuck to it.

And he was absolutely right. But then, his adolescence had been lived in the simple, homely 1940s; the only thing he had to worry about was being shot down or bombed by Nazis, and the collapse of western civilisation. I hit the streets in the 1970s, and, you know, it was a war out there. I could have been killed. It’s the memory of my teenage years that makes me so disproportionately hard on Ali. When I let him get a word in, he said I was a hypocrite, because I’d had my ear pierced at his age. Hypocrisy is big with kids. They see it everywhere. We tend to draw a veil: it’s just too awkward an accusation to start chucking around in the glasshouse of the over-thirties. We call it “learning from my mistakes”; “do as I say, not as I did”. I was a particularly awful role model: a drunk junkie and, worse, a vegetarian, without a single certificate or qualification. I was surly and argumentatively whingeing at school, lazy and angry and entitled at home. I know that Ali is a far nicer kid, and better son, than I ever was. It seems like no time since he was a cherubic pink face on a cot pillow, lit by a pale night-light, the blond hair damply curled on his brow; when I swore — as all fathers do — to protect him from harm, to bring him through childhood happy and safe, as perfect and peaceful as he was at that moment. So I mind when someone sticks a needle in his face. I also mind when I realise that my responsibility is almost at an end. Next year, the year after, he’ll be his own guardian, but I will never cease to be concerned, or worry. This lost, retrospective argument about his piercing feels like the end of a long, but all-too-short, shared journey through the woods.

And he is quite right: things, when pierced, can never be unpierced. But it’s not quite over. There’s still one thing I can do, one arrow left in the paternal quiver. Embarrassment. I’m going to turn up at school with a big drop earring.

And Ali Gill on why he won't be browbeaten by his dad . . .

Why shouldn’t teens get piercings? Nothing really bad’s come out of my eyebrow bar, unless you count the blood. I was the first one at school to get it done and everyone thought it was really cool — including my tutor and housemaster. And there was definitely a ripple at a party I went to recently.

It all came about unexpectedly. I was trying to persuade my friend Tom to get one done and ended up promising to get one done if he did. (In the end, he didn’t.) As soon as I got into the tattoo parlour, I did slightly regret it, as there was blood all over the floor, and a girl with her face covered in blood. There was also a sign saying whatever happens, it’s not the staff’s fault. But in the end it was fairly painless — although three days later it came out in my sleep, and sealed up, so I went back and got it re-pierced. This time I felt a cup of blood coming down my face, and a lot of swearwords coming from the piercer. But she halved the price to £10, so I guess it was fine. When I got home, my mum looked at it — normally she just flips when bad things happen — took a big swallow, and just went “Right”. When I told Dad, he went “Oh God”. But I definitely don’t regret it — I met an older person recently who’d had one and let it seal up, and you couldn’t see anything. I might even consider a tattoo, too, although Dad gave me £5 to promise I won’t get one till I’m 21. Although if I did want one, he wanted to design it. That’ll be a penis going up my face, then.

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