In person, Gibbons is strangely slight, wafer-thin in a wizened kind of way. He doesn't loom like you expect. Can this be the creative mainspring of the roughest, toughest, most enduring boogie band in all of rock? A second glance furnishes assurance: the obligatory Ray-Bans are present and correct, even in the crepuscular mid-afternoon gloom of a London hotel room, and the jeans and boots are exactly as expected - but what's that on Billy's head? It looks like a Rasta swimming-cap, a skullcap of short dreads that combines with the leonine tendrils of his beard to give him the appearance of some ancient wizard. Jah Merlin, perhaps.
As it happens, the headgear is sartorial evidence of Billy's recent interest in African ephemera. It's a Cameroon chieftain's hat, one of several artefacts purchased to lend a little atmosphere during the recording of the Top's latest album, Rhythmeen. Like its predecessor, Antenna, the new LP represents a return to the bluesy, "old school" ZZ Top after the multi-platinum synth-driven epics of the Eighties such as Eliminator and Afterburner, and during sessions, the group were searching for a way to re-charge their blues roots and give the music some new kind of context. They found it in a book by blues scholar Paul Oliver called Savannah Syncopators: African Retentions in the Blues, which, upon its publication in the early Seventies, effectively proved the direct connection between African musical forms and customs and those of their New World descendants.
"Since we were classified as more of a blues band than anything, I thought that was where we should go," explains Billy. "But the studio landscape looked exactly the same as for the Antenna sessions - I said, 'Man, either bring in a plate of barbecue, or import some Zulu spears! Give me something to go on!'
"Finding Masai warrior clubs in Houston is a challenge - but somebody went out and came back with masks and things from the Dan tribe and the Dogon people, so all of a sudden we had quite a wide array of handy reminders to keep towards this. And as the music unfolded, a genuine interest developed: we kept returning to these power points, and these peculiar-looking figures started looking familiar. The music was flowing, and I wasn't about to tamper with whatever was going on, because it felt really good."
So much did the interest develop that Gibbons has started attending auctions of tribal artefacts, and searches out pieces for himself when he has the time. He hands me what appears to be a gnarled leather pessary, purchased this very morning at one such specialist shop in the Portobello Road. "This looks like how I wanted our music to sound," he explains with a grin. "I don't know what it was for - possibly some kind of stash purse? - but it's just encrusted with history, patinated and well used. That was the way we were going - away from the perfectly produced, shiny piece; just toss it on the fire and let it burn."
It's yet another category of things for Gibbons to collect, alongside his cars and his modern art. A trustee of the Houston Contemporary Art Museum, he has a taste for surrealism, in particular the work of Salvador Dali. "This cat was out there, and he stayed out there," he enthuses. "Oddly enough, here we are still looking into his work, not only acknowledging it as out there, but willing to go out there too."
So the spinning fur guitars in the ZZ Top video were presumably a reference to surrealist sculptor Meret Oppenheim's famous fur cup and saucer? Billy ponders a moment, then chuckles: "More Bo Diddley!" Art, after all, comes in many strange and wondrous forms, and not all of them are in galleries: some are Texan sheriffs. Indeed, not all of them are readily recognisable as art, even in our post-Warhol age. It's this soft underbelly of kitsch for which ZZ Top are more famed, celebrating in song such staples of American culture as the TV Dinner, the Cheap Sunglasses, the Velcro Fly, the Burger Man, and countless shiny hunks of gas-guzzling Detroit Iron, including the Eliminator custom car and the new album's "Rhythmeen" itself. Asked about his favourite car, Billy strokes his beard awhile, visualising. "In my mind I've got this up-to-date, constantly refreshed picture of the French Quarter in New Orleans, and it's basically a silver Lincoln Continental driven by an inhabitant of New Orleans. There's always something kind of ... not unsavoury, so much as seedy, about it."
For the moment, though, Gibbons is leaning by default towards less delightful transports. The roads of his home town, Houston, he explains, have become so congested and dangerous that he's taken to driving a cheap car rather than risk damaging his more stylish vehicles. "I wound up the proud owner of Ford's least expensive model," he says. "The damn thing has great brakes, rack-and-pinion steering, the AC blows ice-cold - put tinted windows and a good stereo in it, brother, and have at it! I'm gonna write a song called 'Drive a Cheap Ford'!"
What, though, is the basic appeal of American trash culture?
"Well, there's certainly a lot of it! And the real bugaboo is, assuming you're outside of it, to be able to take a posture for comment. Then you start thinking, 'Here I am at the rental car counter, and they're handing me the keys to a silver Continental - am I that seedy guy now?' "
Seedy guy or surrealist art collector, Gibbons has grown more circumspect about his country's apparently insatiable appetite for trash culture, having observed the speed with which novelty now dissipates. "The moment that genuine novelty shows up, the resultant immediacy of diffusion - thanks to the communications media and the Internet and stuff - dissipates it instantly," he believes. "It's really challenging to come up with a long-lasting point of charm. One rather astute writer put it very well: he said there's more evidence of the Egyptian civilisation, thousands of years later, than there'll ever be of ours!"
n 'Rythmeen' is released 9 September on RCA