The comedian Phill Jupitus used to do a stand-up routine about the internet. He talked about how, late at night, when his wife had gone up to bed, he'd sit at the computer "doing the accounts". From the complicit laugh this got from the men in the audience, and the resigned chuckles of the women, it was clear he'd touched on a pretty common experience. Of course, what he - or perhaps his comic persona - was actually doing was surfing for porn. He would think of something, some sexual act, some coupling, tap a description into a search engine and take his pick from the results. The search terms he tapped in got more and more outlandish, but they always returned a huge number of results. It became something of a challenge, to try to think of some sexual act, some depravity, so repellent, or simply bizarre, that no one else had ever thought of it, or at least one which no one had photographed and put on the internet. He failed. However weird the things his imagination conjured up, the internet sent back a flood of responses. I was one of those in the audience who knew exactly what he was talking about, except I didn't call it "doing the accounts". I called it "researching the book".

My contact with the internet began in the most auspicious of ways. In 1999 I was appointed online editor of The Times. I went at my new task with vigour. I spent all day, every day online, looking at what The Times might become in internet guise. The internet fascinated me, I had the zeal of a convert. I was struck by just how radically it could change the world. It seemed obvious to me that the cyber-dollar would become the international currency, English the international language. The internet could make true, grass-roots democracy realisable for the first time. Soon the sum total of human knowledge would be available to all. OK, overblown, I know, but this was at the height of the online bubble when everything seemed possible.

I was also struck by the libertarian ideals of those who created the world wide web. They decreed that the internet must be free: free of imposed values, morals, restrictions. They did not recognise intellectual property rights any more than conventional sexual mores. Online, no one should have to pay for anything. Like revolutionaries down the ages, they spurned censorship of any kind.

I realised there was probably a book in all this, and started work on a proposal. The working title was The Virtual Eden. In the proposal I wrote: "In the Garden of Eden, God told Adam and Eve that they must not eat the fruit from a certain tree. With the internet, there is no supreme being telling us what we can and cannot access. The internet is a Godless Eden. It is down to the individual's conscience what they do and do not look at and delve into."

For some months I really was "researching the book" when I went online most evenings. But gradually I looked more and more at pornography. Then, and even more so now, pornography was endemic on the internet, and I found I had an appetite for it. The more I fed that appetite, the more it grew. Like the man in the joke, I went for more and more outlandish search terms, I looked at anything and everything. The book was forgotten, I was just looking at as much pornography as I could.

Now let's jump forward four years. The doorbell rang at 6.20 on a dark morning in March 2003. We had been asleep. My wife, Elena, went downstairs. I heard voices, then she returned: "Andy, it's the police and they want to talk to you."

There were four of them in the hallway. The one I later discovered was DC Golder asked me my name and then said, "I am arresting you on suspicion of making an indecent image of a child. You do not have to say anything…" I became aware that my daughter was at the top of the stairs and was hearing everything. It felt like the end of my life. I forced myself to listen to DC Golder again. "Do you have any computers in the house?" he was asking. "Is there pornography on any of them?" "Yes," I said, "on my laptop - but nothing illegal."

In a way, I'd been expecting this knock on the door since 1999, but it was still a profound shock. Lately I'd read about Operation Ore, in which the British police had been handed a list of some 7,000 people in this country who had used their credit cards to access child pornography sites through a company called Landslide in Fort Worth, Texas. Indeed, we had done articles and leaders on the investigation at the Sunday Express, where I was now deputy editor. But I had no recollection of going to that site, or buying from it.

The police moved quietly and politely around the house, collecting computers, searching in drawers, through bookshelves and piles of videos. They let me shower and dress. I put on my suit, and packed the day's newspapers into my bag, as if I were setting off for work as normal. My wife was trying to comfort my 15-year-old daughter. My son, 12 at the time, had not surfaced. I went into his room. He was lying rigid in bed in the dark holding the covers up to his chin with both hands. I told him not to worry, that everything would be all right. Neither of us believed me.

They drove me through the back streets in an unmarked silver Astra to Southall police station, where I was locked in a cell, the walls and ceiling painted in blue gloss. I sat on the concrete bed, on a rumpled green blanket warm from the last occupant, and read my papers in a parody of preparation for a morning news conference that I would not attend. It was two hours before Elena was able to locate a suitable solicitor who could get to me. The solicitor told me it all hinged on what the police found on the computers, and as I hadn't - as I thought - saved, stored or catalogued anything but adult porn, I thought there was probably nothing to find. So I was calculatingly noncommittal under interrogation.

Next day I went to work, trying to behave as usual, but by the evening I knew I could not keep up the bluff. I told my wife that among the things I had been looking at were pictures of underage girls. I shall never forget the look of dawning horror on her face. Next morning we told the lawyers, and I resigned from my job. I knew I could lose Elena because of this. We had been married for 20 years but I knew the weight of deception I had perpetrated would test even the strongest relationship. I also knew that social services would investigate us, and although I had never acted at all inappropriately with either my son or daughter - or indeed any other child - we could not be sure that a social worker mightn't think it prudent to remove me from the family, or our children from us.

If I had been an anonymous member of the public I could probably have avoided any publicity for my case. But I worked for Richard Desmond, owner of Express Newspapers, a man with powerful enemies in Fleet Street and beyond. They called him The Pornographer, because he also owned an adult cable channel and, at the time, a range of top-shelf magazines. One or two of those enemies saw me as a convenient - if rather feeble - stick to beat Richard Desmond with, and my name was published.I knew I had to begin from this moment to reconstruct my life.

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