There I was, flipping idly through the channels of my hotel TV, past the American sitcoms, past the shopping channels, and suddenly I'm in a netherworld of horrible plastic bumping and humping. The XXX channels. Look, I'm a writer. I'm not going to shriek and flip the TV off instantly. So I watched for as long as I could manage. Which was about thirty seconds. And then I turned it off, feeling genuinely queasy.

I always wonder why the anti-porn lobby doesn't make more noise. Apparently, between 60 and 90 percent of under-16s view hardcore online porn occasionally to frequently, and the single largest group of internet porn consumers is reported to be children aged 12 to 17.  Which is bad enough on its own, but far worse when linked with stratospheric rises in: teenage girls posting homemade porn online, violence perpetrated by teen boys on their girlfriends, demand for genital cosmetic surgery, sexual desensitisation, a market for ever more extreme images and -- as with drug use -- addiction.

I won't even start about the women making the stuff. Don't tell me it's because they find it empowering.

It's hard to come out against pornography without sounding like a spoilsport. But a GP friend told me she's seeing more and more teenage girls in her surgery covered with bruises from sexual violence they take for granted. "They've come to see me about other things," she said, "and seem surprised and irritated when I ask about the evidence of abuse."

A girl's secondary school across the street in North London asked me to come in and talk about my male characters. "It's a revelation to them that boys aren't always abusive and macho," the librarian told me.

One of the worst things about porn is how phoney it is. Which means that the kids watching it, most of whom have had almost no previous experience of real sex, are learning from a freakily distorted template. Like figuring out what you should look like from the manipulated models on magazine covers. (Watch this, if you haven't seen it. Brilliant.)

I turned the TV off pretty quickly but I can't get that plastic woman with the fake boobs doing an imitation of a frenetic wind-up toy out of my mind.

More evidence that God is a teenage boy. Like we needed it.