We started this investigation when Mark Williams-Thomas approached us. He's been a criminologist and child protection expert for 20 years and used to be a police detective, so he's got a considerable amount of experience in this.
He came to us with concerns about paedophiles operating on Twitter, having previously done considerable work with Facebook. The difference between Facebook and Twitter is that Facebook actively monitors profiles, so they can identify people who they believe are sex offenders and pass them over to the police.
Twitter only close down an offending account, and do not monitor or look into it – so if you close down a profile, the person can just open up a new one.
As the reporter on the story, I was working with Mark. He set up a fake profile, which I had access to as well, and started doing key-word searches to find these individuals. Some of them had open, unprotected profiles so you could just watch them, while others were protected but Mark was accepted to â€˜follow' them.
My role was to record all the conversations we could see, and monitor direct messages he was receiving under the fake profile. I collated the information and worked out who they were and where they lived.
It got to a stage, just a few days into the investigation, where we became concerned by what we were seeing and we took the decision to go to the police. As soon as we became concerned we didn't sit on the information, we called the police. We had a very important responsibility not to sit on any genuine information.
It crossed the line of being suspicious to being very concerning. When it got to that stage we immediately called the police and started working with the [Met's] paedophile unit, passing over everything we had. For the next seven days we agreed to pass the information on and they took charge and made the arrests.
We've now done a follow-up and started a campaign to get Twitter to clean up its act – we exposed it and now we're saying it needs to be tackled. Our concern is Twitter has 500 million users and a large proportion of those are children.
The disturbing feature of it is how easily paedophiles find each other and how easily we found them. We're still working with Mark and we've had a lot of support. It's going to be discussed at the meeting of the UK Council for Child Internet Safety in October, so it is gathering momentum and we plan to carry on lobbying Twitter.
We are the first newspaper to look into this situation. Before I had witnessed what these people were doing, I didn't believe it could be so widespread. But, looking back now, it seems hardly surprising because paedophiles are always looking for new platforms. Twitter is the latest thing.
I've covered a lot as a reporter, but this was the most shocking story I've covered in terms of sex offenders, because it's so wide-spread. It's like an underbelly to Twitter, a parallel road, and these individuals are highly dangerous. That's why the Sunday Mirror is keen to keep this campaign going. Facebook has taken a lead and now Twitter needs to follow.