A lot of very earnest books have been penned about the midlife crisis. But it’s in their forties or fifties that many people also experience a unique moment of joyous relief. I can confidently predict that such a moment will hit me next month. Indeed, I can tell you the date. It’s the day on which my youngest child turns 21.

I am not, of course, naive enough to think that this signifies some sort of light at the end of the tunnel. Some chance! The birthday boy’s elder siblings are graduates, they are earning, and they are in relationships that bring them happiness. Yet they still have days when they seem to want praise, consolation, advice or just plain old unconditional love from their parents. And I hope they always will. It’s nice to feel, as a derided and hilariously untrendy dad, that you still have your occasional uses.

Nevertheless, I hadn’t realised until recently how much you feel a burden lifting from your shoulders when all your kids reach adulthood. It’s not so much the financial burden — though if you think you can get three children from nappies to graduation on less than half a million quid, do let me in on the secret. It’s much more the burden of responsibility.

When people assess what they have achieved in life, they usually focus on careers or hobbies. But the greatest achievement is steering your children safely through the temptations and dangers of adolescence and seeing them emerge — relatively literate, happy, good-natured and addiction-free — as balanced adults. Every parent knows what a hazardous (and often thankless) operation that can be, especially on the mean streets of modern urban Britain.

And if they don’t, the news from the Cornish seaside resort of Newquay last week would have reminded them of how badly, and how suddenly, things can go wrong. In the space of ten days, in separate incidents, three teenage boys fell from cliffs. Two died; a third broke his neck and fractured his skull, but lived.

All, it seems, were “partying”. That is what 16-year-olds go to Newquay to do. My daughter did it, and at the time I remember thinking (innocently!) that the sun, sea and bracing Cornish breezes would put some colour into her pallid cheeks. Of course, she returned looking as if she hadn’t slept for a week — which (it turned out) was exactly the case.

Whatever, Newquay has become one of the most popular rites of passage for British teens. Celebrating the end of their GCSEs, they descend in their tens of thousands on a resort that markets itself as “party central”. The town authorities, the police and the proprietors of the tawdry bars and clubs cluttering the main street all insist that there are checks to stop under-18s from buying alcohol. But anyone who visits the place knows that this is hogwash. Most nights on the beach there is more booze than surf. And the atmosphere on the streets is tacky, raucous, anarchic and terribly depressing. Here are kids who are healthy, energetic, not short of cash and probably intelligent, too — and all they want to do is get “wasted”. Their word, not mine; but it is proving horribly apt this summer.

The parents of the 16-year-old who fell to his death last week are calling for a boycott of the place. If that spurs the town to clean up its act, it wouldn’t do any harm. In its present form Newquay is a blot on Cornwall’s commendable record for modernising and diversifying its attractions and luring families back to its glorious coastline. It has some of the world’s finest beaches (which are, paradoxically, well patrolled during the day). Its 200ft cliffs offer some of the most spectacular walks in Britain. It shouldn’t need to degrade itself by appealing to the lowest common teenage denominator — unsupervised, drunken mayhem.

But I suspect that if Newquay became too heavily policed and sanitised, the partying kids would simply go elsewhere. Newquay isn’t the cause of all this. It’s just the venue, albeit a venue that has sold its soul and squandered its natural assets in a grotesque pursuit of the teenage pound.

The root of the issue is the endemic binge-drinking culture that seems to have taken a grip on large numbers of teenage boys and girls. Those two deaths last week, tragic though they are, must be set in the context of a society in which drink and drug-related accidents and fights fill most A&Es in Britain with bloodied youngsters every weekend.

How do we stop that? Ban booze from being sold to anyone under 21 or even 25, as in some US cities? Tougher policing and stiffer penalties for public disorder? Curfews? A return to some form of National Service, so that boisterous teenage energies can be channelled into worthwhile community activities during those ridiculously long school holidays?

Maybe all those are worth debating. But piling draconian restrictions on teenagers won’t help them to develop their own sense of responsibility and judgment, especially at the very time when they are straining at the leash of parental authority.

As a parent you can only hope that the core values you have tried to instil into your kids — by word and (more difficult) by example — kick in at those crucial moments when temptation lurks. The value of exercising moderation in all things, for example. Of courtesy towards others, especially in public places. Of self-reliance, common sense and trustworthiness. Even then, though, you can’t guarantee your teenage child’s safety at all times. You can’t choose their friends. You can’t vet the clubs where they meet, or impose your view on which areas of London (or Cornwall) to avoid. You are unlikely to be present at that vital moment when they should be reaching for a condom. So, as a parent, there is one other crucial thing you need. A 21-year unbroken run of good luck.

That is what I will celebrate next month — not my brilliant parenting but my brilliant good fortune. Both my sons, in different ways, have had very close encounters with death. But they and my daughter have reached adulthood in one piece, and for that I say a prayer of thanksgiving. The parents of those boys in Newquay have not been so lucky, and my heart goes out to them. There, but for the grace of God . . .

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