Did kidult culture spawn kidult restaurants, or was it perhaps the other way round? Certainly, the concentrated ambience of senile juvenescence that saturates establishments such as the Hard Rock Café, Planet Hollywood and TGI Friday's makes them a suitable vanguard of the kidult revolution. I blame the Sixties. Between the door of TGI Friday's - beside which stood a life-size model of the Iron Man (although, on reflection, is it possible for a fictional superhero to be "life-size"?) - and our table, the waiting captain challenged us with the phrase "All right, guys?" no fewer than four times, as if we were being subjected to a kidult interrogation.

Being a kidult myself, I didn't mind, but Luther, who's nine years old and a bona fide child, was - in his own words - "weirded out". And when another servitor leapt out at him and barked, "What's up, boss!?" he almost burst into tears. In fact, our entire trip to Friday's was in this Vice Versa spirit, with the kid hating every minute and the adult, if not exactly cherishing the experience, prepared to give it the benefit of the doubt.

We were seated between a quartet of Japanese tourists who proceeded to haggle relentlessly over their bill and a Middle Eastern family consisting of black-bagged mum and a dad who footled with his 3G phone. Coyly, Friday's avers that the "G" in "TGI" stands for "goodness", but looking around at the multi-faith clientele babbling under a cloud of hickory-flavoured barbecue sauce, I was certain it could represent either a monotheistic "God" or the entire polymorphously perverse Hindu pantheon.

American nightmare

The decor at TGI is actually a pantheon of Americana - the aforementioned Iron Man, an ET, a drum kit, a Harley-Davidson motorcycle and so on. "One of the things that's annoying me," Luther observed tartly, "is that it's super-American." Then he ordered a jumbo hot dog from the kids' menu. For the duration of our meal, a succession of pop songs percolated through the gloom - you know the ones: Motown stompers, the Small Faces, the Kinks, even Iggy Pop's “The Passenger". None of them was intrinsically bad, but they all suffered by association.

I toyed with requesting one of the special house burgers, but while not going so far as one of my friends who observed, of an anorexic family member, "For her, food is essentially pre-shit," I can't say the idea of seven ounces of beef slathered with guacamole filled me with anything but thoughts of coprophilia. So I settled for the Caesar salad and a side order of shrimps done in the Friday's signature Jack Daniel's marinade. Indeed, were it not for Luther's gloom, I might have fallen further off the wagon than this and abandoned a decade's sobriety by ordering one of the "Whiskey Wonders" - possibly a Godfather, which is glossed as: "A simple combination of Scotch and Luxardo amaretto that's as classic as its movie namesake."

The previous evening I'd had dinner with my nephew, who told me that his girlfriend was constitutionally unable to vomit. I think I'd found a cure. Friday's prides itself on its cocktails: there are pages of such nauseating descriptions, and, as I leafed through them, it occurred to me that really these are the alcopops of a pseudo-sophistication, and that when all's said and puked, there's no fundamental distinction to be made between James Bond's ultra-dry Martini and Vicky Pollard's Bacardi Breezer.

No kidding

Luther pronounced his jumbo hot dog to be "very jumbo", which I think was a compliment. My Caesar salad was bone-cold strips of chicken laid out on a pallet of limp lettuce and hideous croutons. But then, is there anything more hideously inutile than a crouton in this whole wide world? The big surprise was the shrimps - which were surprisingly tasty; I wolfed them down.

All in all, I hadn't minded TGI Friday's nearly as much as I thought I would. It may have been the presence of my depressed nine-year-old, or it could be that I sensed that this was the beginning of the end for kidult dining - after all, with a rapidly declining birth rate, this curious inversion of mores may be about to implode. In the future, with an enormous ageing population, children's birthday parties will probably take place in establishments like the Palm Court at the Ritz, with string quartets instead of guitar bands. One can only hope.