As invitations go, it was certainly provocative. Would I be interested in being an extra in Dirty Mind, a fantasy-based porn movie? The recording of the film, which was destined for Richard Desmond's Television X, was due to take place at a central London bar, and essentially revolved around a woman's fantasy about having a shag in front of 20 other punters. The idea with the extras was that we would people the bar, drinking, smoking and generally being chatty while sex was going on at elbow-height. As you do.

In the e-mail, it was explained that although the main protagonists would not be "acting" as such, because they would be having sex, we would not be required to. Have sex, that is. We would be required to do a bit of acting, though. To make it look natural.

I called the sender of the e-mail. I know him rather well, him being an ex-boyfriend from college days, though I have seen him only twice in the past two decades. Was I surprised he has a deal to supply Desmond with 40 X-rated films over the next year? Not really. He always did have distinctly exotic tastes. When we weren't tying each other up with hosiery, we were putting on Sam Shepard plays and Restoration comedies - but drama is drama, even if it involves taking your clothes off on a bar top in central London.

In the business of porn, he says he's doing well. There's a sort of ski-slope style of progression in the porn film-making community. This year he is on soft-porn blue runs. Next year he moves up to the black runs of hard-core.

Two things were striking about the conversation. First, he had invited only women along. "I've told people they can bring a male friend along if they want," he explained. "But I want to lead with women, because if you start inviting men, you end up with crowds of drooling blokes, which I absolutely do not want." Women, it would appear, know how to conduct themselves during a porn shoot. Perhaps it's an instinctive skill. Second, he was keen to stress that my participation would be "for a laugh", and I found myself readily concurring.

It seems that, outwardly, the only proper reaction to porn is to see the funny side of it. I mean, you don't want to seem like a prude, even if you might be shocked inside. Or, indeed, turned on. Once I had wiped the tears of mirth from my eyes, I asked him if he had read Martin Amis's coruscating account of the LA porn industry, where an air of violence and subservience lingers, if not on the surface, then just under it. "Oh, don't believe everything you read about the porn industry," he said. "It's just like any other business. My make-up girl does shoots for cover stars on the Radio Times. Then she comes along and does our people. It's cool."

So was I tempted? Observant readers will have noticed the temporary disappearance of this column at the end of last year. I only got the invitation when I logged on this week, back in the NS office after a break having a baby. And the shoot was in early December. Would I have gone along? It's unlikely. Childbirth is a messy and emotional enough activity, and involves quite enough grunting for the time being, even if it is in some way fundamentally linked to the activities on the bar top.