We often think of ourselves as the heroes of our life stories but how many of us actually live up to that, asks Anthony McGowan.

There's a sketch by the comedians Mitchell and Webb in which a couple of SS officers are preparing to face an attack on the Eastern front. On noticing, as if for the first time, the skull and crossbones on his cap, one asks the other in a perplexed sort of way: "Hans, are we the baddies?"

It's a funny line and gains much from Mitchell's habitual air of baffled innocence. But it also has a deeper resonance and compressed within it are profound questions about history, about geopolitics, about the nature of the human soul itself.

There is, of course, an almost irresistible human impulse to look on ourselves as the goodies or - with a little more grandiosity - as the heroes of our own narratives, whether we're fighting over the height of our neighbour's leylandii hedge or authorising air strikes on crumbling dictatorships.

Find out more Anthony McGowan is an award-winning author of novels for young adults and teenagers

His episode of Four Thought is on BBC Radio 4 on 14 December, 2011 at 20:45 GMT Listen again via the BBC iPlayer Or download the podcast

I strongly suspect that all of the monsters of history, from Attila to Saddam, by way of Stalin, Hitler, Mao and Pol Pot, have viewed their actions as in some way ethical, conforming to a moral code, be it religious, tribal, Nationalistic or ideological.

And the lesson of this is that it's always worth interrogating our motives and that, in fact, our interrogation should be most rigorous when we are most convinced of the purity, honour and goodness of our intentions.

However, I found that this question - are we the baddies? - had a deeper and more personal resonance for me.

A couple of years ago I stumbled across a photograph on a social networking site. It showed a soldier sitting on the front of a tank in Iraq, with the lone and level sands stretching away on every side. The face looked vaguely familiar. I checked the name. Mark Duffy (not his real name). And yes, it belonged to a kid I used to know at school.

Roland Barthes in his book Camera Lucida talks about a feature you sometimes find in a photo that moves you, some small detail which suddenly interrupts the smooth passage of the eye as it scans across the flat two-dimensional image. It's a point of intensity - what Barthes calls a punctum - and it creates a sort of vortex that pulls the viewer into the secret world of the photo.

Fatal flaw

And as I gazed at the photo of Mark Duffy, I saw that there was a smudge of something on his face. Oil or dirt. Not blood, I don't think. But most definitely a punctum.

And suddenly I was drawn back through the vista of years to our old school, Corpus Christi in Leeds. Corpus served the huge and impoverished Halton Moor estate - a byword for urban despair. Bullying was endemic, along with a generally high background level of brutality.

Image caption Would you help if someone was being bullied?

It was a tough environment to survive in and you did it with the help of your friends. My gang was a group of nerds and misfits, potential bully fodder. We should have been preyed on by the hard kids, dead-legged and spat on, our dinner money stolen and our satchels thrown over the school fence.

We weren't, only because the hard kids were frightened of Chris Rushby, the unchallenged leader of our little gang. Chris didn't really belong with us. He was from the local estate, so he was tough as tungsten, but he wasn't one of the meat heads. And for some reason he liked me. We got each other's jokes, felt easy together.

And the key thing about Chris, the truly unusual thing, was that he was good. His goodness was why he let Mark Duffy come into our lives.

Duffy was a colourless, pasty kid, with grey teeth and skinny legs. He had no chat, no jokes, no panache. But Duffy's biggest fault, his fatal flaw, was having a mother who loved him. One day in the very first term of school his mum dropped him at the school gates. That was bad enough. But then she did the terrible thing. Right there, with a playground full of wolves and hyenas and jackals looking on, Mrs Duffy kissed him and left a set of vivid red lips on his white cheek. My punctum.

She might as well have stabbed him in the heart with a screwdriver because from then on it was open season. He'd be punched and kicked by anyone who felt like it. The tiny minority who didn't bother hitting him ignored him.

Betrayal

Some of us should have seen him, helped him. But that would have contaminated us with his deathly, ghostly stink. And then Duffy was given a glimmer of hope. It all began when Chris let Duffy eat his sandwiches near the five of us who always ate our sandwiches in an alcove in the school wall.

Normally we would have stoned Duffy like a pariah dog and driven him away, but Chris started talking to him. And before we knew what was happening he was in our alcove, sharing our warmth, stealing our cool. I didn't like it. Partly it was the fear that Duffy was going to make us a target. Partly I was jealous.

I suspect that my betrayal of Duffy changed how he thought about me, about us, about the nice kids... we were no better than the brutes

Then Chris told Duffy he could come with us after school to mess about by the stream that we called "the beck". It wasn't some babbling brook, full of fish and tadpoles, all sparkly with white water. It was brown and oily and it stank like a chemical toilet. But for us it was a place of adventure, excitement and enchantment.

For most of its length the beck was too wide to jump, but there were a couple of spots where you could leap with a good chance of a safe landing and you couldn't beat it. That sense of freedom as you jumped.

Of course Duffy had never been one of the beck jumpers. And I wished that he had some other friends of his own to do stuff with. But now he was with us. Ruining things. It had to end.

At one of the beck's widest, deepest parts, it formed a sort of a pool. And that's where someone had dumped a fridge. No-one had ever jumped over the pool before. You'd need to be some kind of Olympic champion to do it. But I'd wondered if maybe a kid could jump from the right hand bank, land with one foot on the fridge and then take off again, landing safely on the far side. But the fridge wasn't stable.

I knew it wasn't because I'd poked it with a stick. Anyone landing on it would fall into the poisonous filth. So now I sidled up to Duffy.

Laughter, shouts, jeering

"There's a cool place to jump. Up at the pool. You have to steppy-stone on the fridge. It's not hard - I've done it. Chris'll think it's cool." He looked up at me. "OK."

"Duffy's jumping the fridge," I screamed at the others, leaving him no time to change his mind. Duffy took off his blazer and gave it to me. Chris was telling him what to do. Duffy now smiling, nodding. He looked happy for the first time since his mother had kissed him two years before.

Duffy prepared himself, he ran, he jumped. I couldn't see his face, but I could imagine it. And I have imagined it, many times. He'd left it all in his wake, the years of horror, the beatings, the dog mess smeared on his blazer - all that. He was a butterfly shuffling off the dry, brown cocoon, becoming beautiful.

Image caption People can change from heroes to villains

And then Duffy's foot came down on the fridge and the fridge, as it was meant to do, betrayed him. Into the water he fell, his face contorted with surprise and fear. Of course everyone found this hysterical. Laughter, shouts, jeering.

We didn't even look as Duffy dragged himself out of the beck. But I noticed an odd thing, Chris didn't help him. He just stood there and watched, his face blank. Then he walked away, across the rough Gypsy Field to the council estate where he lived.

Afterwards, Duffy walked alone up to his bus stop. He never sat with us again at lunchtime and Chris didn't try to encourage him. And then he fades from my memory, but I have an idea that he found some others like himself.

Chris himself stopped hanging out with us. I suspect that my betrayal of Duffy changed how he thought about me, about us, about the nice kids. We were no better than the brutes. He became one of them, one of the brutes. He dropped out of school and spiralled down into a place of impossible darkness, too distressing to relate.

But Mark Duffy's story was happier. He ended up in the Army, posting his picture on the Friends Reunited website, with that smudge on his cheek, so like the fatal mark left by his mother's kiss.

And now we're back where we started, with that question. Are we, am I, the baddies? And the answer? The answer, of course, is yes.

This is an edited version of Anthony McGowan's Four Thought broadcast.