Almost every day a politician comes onto the news and tells us all that Britain’s town centres are being overrun by teenage gangs who drink vast quantities of cider and then run about all night stabbing passers-by. While the event is videoed on mobile phones for the edification of YouTube viewers.

It all sounds frightful, but frankly they could be talking about events on the moons of Jupiter because, happily, I live in Chipping Norton, where a lost kitten is front page news. Of course there are teenagers here, and some of them have hoodies, but mostly they are called Araminta and Harry, and I’ve never once got the feeling they want to plunge a kitchen knife into my heart.

It’s the same story in Notting Hill, where I spend the working week. While dining in restaurants such as E & O, I have no real sense that outside the window, gangs of 14-year-olds are lurking in the shadows, eager to punch me in the face for a moment’s glory on the internet.

Last week, however, I had to go to Milton Keynes. It was my youngest daughter’s birthday and she wanted to spend the afternoon at the town’s snow dome. Directions were sent, and then more, with even greater detail about how this indoor Alp might be found. But none of this was really necessary, because you just head for the largest building ever created by man.

It’s a brilliant place, all full of snow and vending machines offering energy drinks. But sadly, because of Mr Blair’s smoking ban, you have to go outside for a cigarette, which puts you slap-bang in one of the happy-slapping town centres the politicians keep talking about.

I wasn’t even remotely bothered when the swarm of children first approached. I figured they were fans of Top Gear and wanted to know about Richard Hammond’s head. But no. What they wanted to know most of all was if I had any security.

I asked them politely to leave me alone. I walked away. I even walked away a bit more. But they kept coming. And so, figuring that attack was probably the best form of defence, I grabbed the ringleader by his hoodie, lifted him off the ground and explained, firmly, that it’d be best if he went back to his tenement.

He declined. They all did. In fact they all reached for their mobile phones and began to take pictures of the altercation. And that put me in a tricky spot . . .

I have reached the age where I am no longer able to tell how old a child is. The boy I was holding could have been 18. Or he could have been eight. And if he did turn out to be eight, I figured the photographs could look a bit like bullying.

So, weirdly, I was standing there holding this boy by the scruff of his neck, and instead of worrying about being stabbed I was actually thinking: “Jesus, I’m going to get done for assault if I’m not careful.”

I therefore put him down, and in a flurry of swearing and hand gestures involving various fingers he was gone. Leaving the entire nation with a very serious problem.

It’s this. Plainly this boy’s parents are useless, allowing him to be out and about on the streets, harassing passers-by at will. Think about it. Every single time one of these children is found stabbed or shot, his mum and stepdad always tell the papers he was a “good lad”. And that he “didn’t deserve to die”.

And nobody ever says: “Well, if he was such a frigging angel, what was he doing on a derelict building site at four in the morning, you halfwits?” He didn’t deserve to die, for sure, but you do, for having the parenting skills of a Welsh dresser.

There’s an equally big problem at school. Children, as far as I can see, are at liberty to do just about anything to one another at school because there is absolutely nothing the teacher can do. Not without being hauled out of the classroom by some frizzy-haired human rights lawyer, sacked and sent to prison.

The police? Oh come on. They are far too busy filling in health and safety forms and processing speeding tickets to be bothered with every single gang of teenage ruffians. Which means that every single gang of teenage ruffians is completely free to go out and do whatever it pleases.

And we – the normal people who see town centres as somewhere to go to buy takeaway food or organise a loan for a new house – can’t do anything either because a) the politicians keep telling us all these kids are tooled up like special forces hitmen, and b) if we stand up for ourselves we will spend the next 40 years in the Scrubs fighting off the unwelcome advances of Pinkski, the Albanian nonce.

Happily I think I have a solution. Nothing can be done about the parents because they are too thick. It’d be like trying to train a hedgehog to smoke a pipe. We can’t rely on the police either – not without unpicking every single thing done by new Labour in the past 10 years.

And, I’m sorry, but even if the law is changed so that adults are allowed to defend themselves, you’d think twice about poking a boy in the eye or slamming his head in a car door if you thought his friends had machetes down their trouser legs.

The only place where this issue can be tackled, then, is at school. So you fit airport-style metal detectors at the doors to ensure no pupil is packing heat, you put all the troublemakers in one class and you give the teacher in charge immunity from criminal charges. And a sub-machinegun.

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