England: The toddler in front of me was rocking back and forth in his seat, screaming periodically. ‘Come on now, Justin, what did we say about sitting quietly?’ his mother cajoled. ‘You’ll spoil it for everyone else.’

But Justin wasn’t even pretending to listen. He stood up on his seat and proceeded to clamber over the other theatre-goers, re.

His mother apologised profusely and tried to follow him along the row, pleading with him to return to his seat. He didn’t. His reign of terror continued for most of the performance.

This week, I took my nephew to see a play, aimed at two to five-year-olds. He sat through it without a murmur, but others were atrociously behaved: hitting, shouting, throwing things. At times I wondered if I was at the theatre or the zoo.

So many of the children lacked any real discipline. Their parents tried reasoning with them — but, being toddlers, reason doesn’t always work.

I wondered what my own mum would have done if I’d been behaving like that as a child. I knew the answer. One warning, then, if I did it again, trousers down, a slap on the back of the legs. Simple. I know it’s a cliche when people say they were smacked and they turned out OK — but I was smacked, and I did turn out OK.

Yet in recent years there have been very vocal campaigns to criminalise any physical chastisement of children. Just this week, the day after I’d been to the theatre, research was published suggesting smacking toddlers risked turning them into aggressive teenagers.

Again, campaigners pounced on this, but a closer look at the study showed it examined severe punishment. No one is advocating that. A smack when you’ve been badly behaved is not the same as a beating.

We know from behaviourist psychology that punishment can help when it comes to changing bad habits. For some, reward works; but for others, punishment is more effective.

This has been well established since the Thirties. The key thing is that it’s the behaviour, not the child, that’s punished — and when applied consistently, the child learns to modify their behaviour.

Besides, if smacking a child causes such deep-seated psychological damage, then we would have a generation of older people who are deeply damaged delinquents and a generation of wonderfully behaved, emotionally well-balanced youngsters. And that’s just not the case, is it?

Certainly, scientific studies don’t back up the idea that smacking is damaging. A few have shown that it can damage children, but there are just as many that show it does no harm.

In 2013, a comprehensive review of published evidence concluded that smacking a child does no long-term psychological harm provided they know that it is for a particular reason and, above all, they feel loved. It’s an important caveat. I knew as a child that when I was naughty, I’d get a clip round the legs, but overall that my parents loved me. I might not always have understood why what I did was naughty, but I always knew my parents had my best interests at heart.

Small children don’t understand so many of the complex rules that govern life and keep them safe, and it’s unreasonable to expect them to. Sometimes, a sharp slap gets the message across just fine.

However, when I said I wanted to write about this topic this week, my poor beleaguered editor nearly choked. ‘You can’t write that it’s OK to smack children — you’ll get inundated with hate mail,’ she reasoned.

And it’s true, I probably will. But why? I’m not advocating sending children up chimneys or down the mines. No one’s saying you should waterboard your toddler into submission.

And, actually, isn’t it the attitude that you can’t even raise your voice to children in case it somehow damages the fragile little flowers that means a generation of badly behaved, over-noticed snowflakes is growing up ill-equipped for dealing with the real world?

I see this in young patients sometimes — those now in their late teens. They simply haven’t developed the necessary coping strategies because they have always got their own way. And I’m afraid this contributes to their mental health problems.

If you let someone grow up thinking they can behave the way they want and that their actions don’t really have consequences, surely that is by far the most damaging thing we can do to a child.