It was no joke for me, ambushed by Ali G

Don't talk to me about chic. I have been on The Ali G Show. It was quite fun being stitched up. The scene is familiar: presenter, three "experts". We were hugger-mugger, arse-down, knees-up on the kind of sofa you can't get out of. He sprawled, like any tall young man with attitude. He threw out questions about animal rights which were very funny. Like (I'm improvising a bit): "Do you approve of testing drugs on animals? Isn't it a waste of good heroin?" Or: "Battery hens? Why do they wire up hens to batteries?"

One looks a prat, of course. That's the idea. But various people who I think are cool have rung me up to say that this encounter means I am now very cool indeed. So everything's fine then. Not quite. Ali G is part of a television fashion which is not half as productive or fun as people think. Let's call this genre ambush television. It depends on getting the drop on people. This segment did that two ways round.

Everyone knows by now that Ali G is not whatever he pretends to be. But it was not like that last spring when I was phoned by your normal-sounding yoof programme researchers to see if I'd appear (I think the next day) in an educational show. Our host was clearly and repeatedly advertised to me as being a disc jockey from Shepherd's Bush who hadn't had much formal education and who might ask some surprising questions on our chosen subject. There wasn't the slightest clue that this was a comedy show. The point is, we were tricked when no one knew about this scam, and the result was screened when everybody did know it.

You will say that anyone might have guessed that Ali never did look the conventional Rasta, let alone tyro television presenter. But we didn't meet "Ali G" until the moment of recording. He disappeared during one short break. He didn't join us in the broom cupboard gloom of what passed for a hospitality room. Within a few minutes of filming, I had more or less tumbled the ruse.

Still, I have been schooled by liberalism not to judge racial books by their covers. I didn't know that Ali G was really Sacha Baron Cohen, a sort of latter day Ben Elton. I thought the Lion of Judah pendant sort of figured. My mind did a little spin about the crossover between Islam and Afro-Caribbean thinking. Might that explain this Asian-seeming fellow? Even then, I wondered if trendy Channel 4 would risk working with a genuine naif? Or were they taking the mickey out of him, not us? Indeed, when I watch Ali, I wonder just who this joke is supposed to be about.

As we got deeper into the hour or more of "as live" taping, I was pretty sure that no one could be this stupid or ignorant. The bottom line was: what if I challenge him? I concluded that the best, or the only, thing was to answer his questions on their face value, and stuff the nuances some editor might graft on later.

I certainly feel for Lady Chelsea, for whom Mr Baron Cohen adopted a new disguise which reclaimed the Ambush Factor in his comedy. Lady Chelsea, a semi-professional adviser on etiquette, told the Mail on Sunday that she feels a bit aggrieved, and wishes she had been more street wise. She shouldn't worry.

She came out of it as a nice, sensible, West End sort of a woman. She didn't sneer at this impostor half as much as he, and perhaps the sillier bits of his audience, sneered at her.

As I say, I quite enjoyed myself on The Ali G Show. I am a sucker for the greasepaint anyway. I am what passes for a professional in this game. And I was delighted to hear that one of my fellow guests has come round to it all as well. "I hated it at the time," says Elizabeth Dyas, who runs a hedgehog hospital. "I thought it was so stupid. But any publicity is welcome, and I've named a hedgehog after Ali G."

Besides, she adds: "My daughter says, it's really cool to have been on." Agreed. But we won't get far if the media, and worse, its audience, believe that any poor sap is fair game for media coshing.

The author is the Media Fellow of The Institute of Economic Affairs