I am just settling into my deckchair when who do I see coming along the beach but Thark, the intergalactic cultural critic from the planet Drong.

Before I can duck behind my newspaper he speaks: "O Great Philosopher, I trust I am not disturbing you?"

"No," I say bravely. "I am just cogitating on a conundrum that has been preoccupying my mind for weeks. Have you noticed that the popular icon Crazy Frog has a navel? Now my biology isn't all it might be, but I don't think frogs have umbilical cords. Still, that's my problem, not yours. How may I help?"

"Well," says he, "on the way here I passed through a city called London, on the other island of this puny archipelago. And in the Sloane Square locality I kept seeing large ostentatious vehicles and heard them referred to as 'Chelsea Tractors'. And I was told by a Sloaney pony called Petronella that you can even buy cans of spray-on mud, in order to give them 'that authentic Countryside Alliance look'. Do these preposterous behemoths roam here as well?"

"Yes, indeed they do," say I, "but we don't call them Chelsea Tractors. They go by a number of names."

"Pray enlarge."

"Well, some people call them 4x4s. You see, four times four is 16, which is the rough intelligence quotient of the average owner. Then there's Off-Road Vehicle. This is because they are found to be particularly essential for negotiating the tricky terrain round the Stillorgan shopping centre. Finally, there's SUV. This stands for Suburban Underclass Vehicle, because that's who drives them, the SU. The SU have mutated spontaneously in the last couple of decades from our own people.

"And, until they acquired in recent times a measure of unaccustomed affluence, mostly by working in the quantitatively-based sector of our economy, these SUs had no idea who they were."

"Quantitatively-based?"

"Yes, you know, the more you manufacture the better, the more you sell the better. The greasy-till tendency. As opposed to the qualitatively-based sector of our society - the doctor, the teacher, the cleric, even, dare one say it, the better class of journalist. You see, my dear Thark, we here are still in many respects a peasant people.

"None of us is far removed from the lavatory at the end of the yard, and all the residual instincts of avarice and suspicion persist.

"So now that some people have acquired an unprecedented level of affluence, they aspire to 'sophistication' and 'cosmopolitanism', and are racing like hell to catch up with those societies that developed these dubious qualities many decades ago.

"By contrast with the SUs, the authentic Suburban Class lives in a pebble-dashed, semi-detached house in a quiet avenue. In his working life he attained a slightly above midlevel rank in a branch of the public service and now enjoys a modest but adequate retirement pension.

"He drives a 1998 Nissan Micra. When the kids were young the family took holidays in Courtown or Kilkee.

"At the moment the SUs are merely in emulative mode, having not yet constructed a personal canon of taste, values and discrimination. I suppose they might make it in two or three generations, but first they have to develop a sense of their identity.

"In the meantime, lacking this, they seek to define themselves by their top-of-the-range German car, their grotesquely overpriced house, their Barbados holidays, the bought-for-rent flat in Budapest, the account in Brown Thomas. These are the Suburban Underclass, Thark, and they are not a pretty sight."

And neither, alas, are their gas-guzzling tanks.

Godfrey Fitzsimons