Image copyright ALAMY

There are many types of people who have been demonised in the age of social media - computer users who take refuge in anonymity to post extreme or offensive views. Jamie Bartlett wanted to talk to the people behind the masks.

My heart was pounding as I waited for Paul to arrive at the train station where we'd agreed to meet. I'd been communicating with him for some time, all via the internet. Paul was a vitriolic, aggressive neo-Nazi who spent his life online producing and sharing White Pride propaganda.

He was one of several people that I spent much of the last year meeting while researching my book. I'd gone in search of shocking and hidden internet subcultures, immersing myself in digital worlds of self-harming, of drugs markets, of internet trolls, of convicted online sex offenders, of digital neo-Nazis.

We often hear in the news about these dangers of life online. But the protagonists in these strange underworlds are always missing from the story. I wanted to find, meet and understand the people behind the screen. That's why I'd come to see Paul.

Fifteen minutes late, a handsome, friendly and earnest young man rocked up - excited to meet Jamie "who I've seen off the telly". He had tattoos, true, but of the trendy variety that climb up necks towards faces, rather than scowl menacingly from thick forearms.

Was this really the digital iconoclast who earlier that day had been attacking and terrifying minorities from behind his sinister looking avatar? Because this Paul was good company - polite, attentive and quick to laugh. We got on very well.

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Jamie Bartlett is director of the Centre for the Analysis of Social Media - this article was originally broadcast for BBC Radio 4 as part of the Four Thought series

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Paul and I spent the day walking around his mid-sized, depressed, Northern town and he told me about his life. In 2011, Paul didn't care about politics. He preferred clubbing.

Then he heard about the anti-Islamist protest group the English Defence League after one of his mates had "liked" them on Facebook. He "liked" them too and started contributing by writing comments on their Facebook page.

Paul has a sharp wit, and is good with words. Within a few weeks he'd been invited to become the administrator of an EDL Facebook group, which gave him the power to delete other people's posts, resolve disputes, and manage the group. (This job, by the way, usually shortened to "admin", is an increasingly important one in modern politics).

Being an admin was possibly the most meaningful position Paul had ever held. People listened to him. He had some respect, power, affirmation. He loved it and spent most of the day there. He devoured articles that others in his group had posted, or that he found himself, about the danger Islam posed to the UK.

He started attacking Muslims on other Facebook pages, and they attacked him back. Each side polarising and radicalising the other. Paul was living in an exciting Manichean world of friends and enemies, right and wrong - in which he was the chief protagonist. Within a couple of years, he was calling Anders Breivik, the far right terrorist who murdered 77 people in Oslo in 2011, a "hero".

One evening he walked past a group of EDL supporters - an unusual scene in his small town. But he didn't speak to them. Online he was a respected member of the nationalist scene, with friends and supporters from all over the world. The real Paul was an unemployed, nervous thirtysomething living alone. Little wonder he kept his head down, walked past, and logged back on to his computer.

Image copyright PA Image caption The EDL relies on social media to recruit followers

There were two Pauls, and that allowed him to behave online in ways he wouldn't have offline. This phenomenon was first spotted in 2001 by the psychologist John Suler. He called it the "online disinhibition effect".

From behind a screen we don't look at or even think about the people we communicate with, and so feel strangely free from the social mores, norms and rules that ordinarily govern our behaviour.

Perhaps the most disinhibited of all is the internet troll - those people who take pleasure in offending or insulting strangers via the net. "Trolling" has become shorthand for any nasty or threatening behaviour online. But there is much more to trolling than abuse.

Zack is in his early 30s, and speaks with a soft Thames Estuary accent. I met him in a pub, where he immediately struck me as one of those sharp, thoughtful, well-read autodidacts - tinged with natural shyness.

He's been trolling strangers for a decade.

"Trolling is not about bullying people," he explained. "It's about unlocking situations, creating new scenarios, pushing boundaries, trying ideas out, calculating the best way to provoke a reaction."

Zack has spent years refining his tactics. His favourite technique is to join an online forum of a group he doesn't like, intentionally make basic grammatical or spelling mistakes, wait for someone to insult his writing, and then try to lock them into a brutal argument about politics.

He showed me one recent example. He'd posted an innocuous, poorly written comment on a popular right-wing website, complaining that right-wingers wouldn't be right-wing if they read more. An incensed user responded, and posted a nude picture that Zack had uploaded to an obscure forum using the same pseudonym some time before. Zack then posted a series of explicit videos of himself interspersed with insults about right-wingers and quotes from Shakespeare and Cervantes.

Zack told me this was a win. "He was so incapable of a coherent response that he resorted to digging into my posting history for things he thought would shame me, but I'm not easily shamed, haha."

"But I thought you were trying to expose far right groups?" I asked.

"By posting the naked photos the discussion drew attention from across the site," he replied. "That is what trolling is all about - creating a scene in order to get more people to think about the issue being raised."

"And do you think you succeeded?" I asked.

"I dunno, but it was fun."

Dealing with trolls

Image copyright Thinkstock

"As the months wore on, he became utterly obsessed. He started posting links full of abuse to my wife, mother and work colleagues. My newborn son even garnered a few mentions."

Richard Bacon: My battle with internet trolls (March 2012)

There are many species of troll. Some like to bully strangers to make themselves feel good. Others get caught in the mob mentality, relentlessly targeting someone to fit in with the digital pack.

But for the thoughtful ones like Zack, it's a mixture of sport, philosophy and - admittedly peculiar - political activism. Zack, you see, thinks people need to be tough and independent, to take responsibility for their actions.

He fears a silent and obedient society, where everyone takes themselves too seriously, and is too easily offended. This leads to self-censorship, and the death of free expression. Trolls like Zack see it as their role to prod and probe the boundaries of offensiveness to keep society alert.

Sometimes online disinhibition takes people places they didn't plan. Like Michael, an approachable but serious man in his 50s, who's happily married with one daughter. "A successful business man, and a completely normal heterosexual bloke" is how he described himself.

Just before I met him, Michael had been convicted of possessing 3,000 illegal images of children on his computer hard drive - mostly girls aged between six and 16.

Like many people convicted of possessing illegal child abuse images, Michael had stumbled into this wickedness. He says he started by viewing legal pornography - women in their early 20s - but kept being offered automatic pop-up windows of girls aged 15-18. This incidentally is more common that most of us would like to admit - "teen" and "young" are the most popular search terms in legal pornography.

At some point Michael clicked, and kept clicking. Over the course of a few years he slowly descended - to 14, then 13, then 12. And kept going. "It happened in tiny increments," he told me, with tears in his eyes. "I really don't remember when I moved from teens to children."

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Image copyright Nick Lowndes

It was the UK's biggest ever computer crime investigation. Thousands of people were accused of downloading images of child abuse - some were found to be innocent. The legacy is controversial. Thirteen years after the raids began, has Operation Ore really changed the UK?

Paedophile net: Did Operation Ore change the UK? (December 2012)

Michael considered himself a deeply moral man, and repeated several times that he'd never harm or hurt anyone, especially not a child. "It didn't seem real," he said. "They always looked like they were not being harmed. I made excuses in my head as to why it was OK. [For a while I told myself what I was doing wasn't even illegal]." He'd become so inured to the images he was viewing, perhaps so addicted, that he'd lost his moral compass, while lying to himself that he still held it firm.

"Why was it so easy for me to find?" he asked me, just before I left the cafe. "If it hadn't been for the internet, I never would have even thought about this stuff." I think he was genuine. With incremental steps, it's easier than you think to end up somewhere you had no intention of going.

"Technology is neither good nor bad," Kranzberg's First Law of Technology tells us, "but nor is it neutral." The internet lowers barriers, making it easier to sate every curiosity, to make it less difficult to say and do things we wouldn't in real life. Sometimes that allows us to explore deeply held desires, sometimes it stimulates behaviour that otherwise would have remained dormant. Often it's somewhere in-between.

I'm not making excuses for these people. I'm aware of the misery they have caused, and that whatever the internet has allowed, in the end they are responsible for their actions and behaviour. Whether they know it or not, these people have caused devastation for others. And certainly there are far worse characters hiding online than these three, using the anonymity the net provides to destroy people's lives.

But they aren't always the evil demons you might imagine. It's important to understand how people end up where they do, without condoning what they do. That may help us limit the damage they cause.

But it's not just them - it's us too. In his essay Looking Back on the Spanish Civil War, George Orwell wrote of being confronted with an enemy who was fleeing while trying to hold up his falling trousers. "I had come here to shoot at 'Fascists'," he wrote, "but a man who is holding up his trousers isn't a 'Fascist', he is visibly a fellow-creature, similar to yourself."

Most of the chief protagonists in my book I met online first, and offline second. I always liked them more in the real world. By removing the face-to-face aspect of human interaction, the internet dehumanises people, and our imagination often turns them into inflated monsters, more terrifying because they are in the shadows.

For me, at least, meeting them in person re-humanised complex, awkward, and usually annoyingly likeable people. Next time you come across a digital monster, remember there is a person behind the avatar, and he or she is unlikely to be how you imagine.

As Paul and I said goodbye that grey and grim November afternoon, I stood a while and watched him wander sadly towards his equally grey and grim block of flats. As the train rushed me back to my self-satisfied life of friends and fulfilment and promise I received a text. "Great to meet you Jamie, I really enjoyed it."

"Me too," I replied. And I meant it.

This article is based on an edited transcript of Jamie Bartlett's Four Thought.

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