Charlie Marley was the haunter of my childhood dreams. He had suckers on his feet. At night, when parents were asleep, he would creep silently along the street and walk up the walls of houses.

Charlie Marley was the haunter of my childhood dreams. He had suckers on his feet. At night, when parents were asleep, he would creep silently along the street and walk up the walls of houses. I knew about him as soon as I could comprehend English because my big sister delighted in telling his story as soon as the lights were out.

"He's coming for me," she would say. "You see that opening?" (Two inches at the top of a sash window.) "He'll slither through there, reach over with his long bony fingers and get me. When you wake up in the morning, I'll be gone." Cue my leap across the (crocodile infested) floor to pinion her to the mattress. Our bedroom was freezing and I suspect I was a more efficient source of heat than a hot-water bottle.

Would Batman have fazed me by the time I was 12 years old? I don't think so.

So why have a record number of adults complained about the 12A certificate granted to the latest Batman film, The Dark Knight? Should we, like Ireland and Scandinavia, have given it a 15 certificate?

If we are to judge by the content of previous 12A films, I can see why we didn't. The Dark Knight contains nothing more frightening than Harry Potter's duel with that embodiment of evil, Voldemort. The violence is no more graphic than in The Bourne Identity, peopled as it is by assassins.

It is far less frightening a film than Jurassic Park, which was a PG. I well remember sitting through it with one of my own children. Such was his terror that he could neither watch nor bear to leave the cinema: he was in and out of the seat like a jack-in-the-box. But, then, Jurassic Park had veloceraptors, a tyrannosaurus rex and two children in mortal danger with tension-building music to match.

Batman isn't like that. Its two and a half hours pass in an enjoyable, action-packed finger-snap. True to its comic-book origins, it doesn't trigger the imagination but spells out its story. If I wanted to carp, I would say it lacked tension and could have lost a couple of car chases. As to the violence, there were one or two moments when I wondered about the 12A certificate - then I reminded myself how grown up a 12-year-old is.

Twelve is only fours years short of a legal marriage certificate and the right to sign up for a tour with the British forces. At 12, a child will probably have watched the evening news before going to the cinema. On it they will repeatedly see real people starving, real people dismembered by bombs in Iraq. They will have heard the details of the Jill Dando killing and of the meaningless, wanton shooting of the honeymoon couple in the Caribbean. They will know about gang culture and the fashion for knife crime. If they live in areas affected by it, they might even live in fear.

Will Batman, with its wild, maniacal Joker, brutalise them further? Will it encourage violence in children? I very much doubt it.

There is a certain disturbing exuberance in the Joker's wild lawlessness. Heath Ledger's viciously playful psychotic performance is heightened by the knowledge that he died shortly after these scenes were shot. His giggling skittishness carried disturbing echoes of Jack Lemmon in Some Like it Hot crossed with the infinitely more frightening Mister Blonde, played by Michael Madson in Reservoir Dogs.

The Joker is mad, reckless, beyond reason and he kills without thought. He is a caricature of wickedness - true to his comic-book origins, he has baddie written all over him. I can see why people might fret about giving children ideas when he despatches one man with a pencil through the eye. However, it happens so fast, with the impact off-camera that it leaves as much or as little impression Tom and Jerry do when they crown one another with frying pans.

More disturbing are the moments when the Joker sticks a knife into someone's mouth and threatens to slice them a smile like his own. That did have me wondering about copycat behaviour - but by those over 12, not under it.

What the film didn't do was to dwell on these incidents. They flashed past in the general action-packed whiz-bang extravaganza.

The Joker does have the best lines. He is witty where Batman is stolid. He craves chaos while Batman his obsessively ordered. While Batman looks for the good in others, The Joker delights in provoking people to give in to the dark side of their nature. Sometimes he even succeeds.

But the essential difference between The Dark Knight and a nihilistic film like No Country for Old Men is in offering hope that in the on-going battle of good against evil, good will triumph in the end.

Hope is all that it offers; not certainty. The other message this film sends is that if evil is to be defeated, well-meaning men have to make sacrifices.

The Joker winds up with the joke on him. It's Batman who emerges battered but unbowed, the unsung hero.

It is the age-old story retold. It is the story of Lord of the Rings and the Northern Lights. It's the theme of The Lion, the Witch and the Wardrobe. Is the Joker any more terrible than the spectres that pursue Frodo; is he any more violent than the beast-like armies of Mordor? Will he cause more nightmares than soul-sucking dementors?

Even Casino Royale, the most recent James Bond film, received fewer complaints about its 12A categorisation. Yet it was far more disturbing. Its hero was a deadly attractive killer, almost devoid of conscience. He made it quite clear that despatching his targets in close combat was a part of the job that didn't bother him.

When his beautiful, young, one-night-stand girlfriend wound up tortured to death in a hammock, M cautioned Bond not to be upset before remembering: "That isn't your problem, is it James?"

Let's not forget that the first tales we tell our children are of child-eating ogres who live at the tops of beanstalks and child-eating wolves who impersonate granny. They graduate to stories of wizards and witches and - if they're lucky - to books (and films) such as A Series of Unfortunate Events by Lemony Snicket. Not since David Copperfield and Oliver Twist have small children endured and survived so many hazards.

We are right to be selective about what children see and hear but in the imaginative world, as in the physical one, we also need to have faith in them. Children have a way of extracting the message from the story and dismissing the special effects. The message Batman sends to 12-year-olds is a good one.