Pink Floyd and their design guru, Storm Thorgerson, have always shared a gently warped vision. A new Floyd boxed set includes a book about their work together - from airborn pigs to 800 beds on a beach. "Art", he tells Martin Aston, "is about flights of the imagination."

"I like pictures that don't necessarily haven an explanation off pat," Storm Thorgerson says of the beguiling sleeves that cemented the reputation of Hipgnosis, the design group he co-founded in 1968. "I remember the idea for Led Zeppelin's Prescence which was to Tamper with nostaligic pictures of the '30s and '40s with an object from the future, which was basically a funny shaped black hole. To me, it represented Zeppelin power, which people at home, or school, would have to have a blast of every few hours, like the ultimate drug. So the design was related to the band, yet extremely tenuou, just as what makes music so rewarding is that it gives you your own pictures."

Hipgnosis came of age in the psyychedelic era, when anything seemed possible. Part of the same Cambridge social set that spawned Pink Floyd, Thorgenson and partner Aubrey Powell's first commission was Floyd's A Saucerful of Secrets, wherein they attempted to mirror three "altered states of conciousness" - religion, drugs, and Floyd music. Yet he denies the not unreasonable notion that drugs supplied some creative surge. "In one's youth," he contends, "drugs, particularly acid, were pivotal in shaping your world view, but no specific style was derived from drugs. I never even smoked dope when I worked. Early on I did a photo session with The Pretty Things, where we smoked a joint beforehand, and I forgot to alter a simple control, and got no pictures at all, which was a bit heavy. You can imagine: 'Hey, Storm, how are the pictures man?' 'Uhh, there's something lacking - like an image.' It was a message from up high."

Either way, Hipgnosis typified the "daily departures from reality" that dressed up prog rock sleevess - The Nice's Elegy, Wishbone Ash's Argus and Zeppelin's Houses of the Holy among them, plus numerous designs for 10cc, UFO, Yes and most famously, all Floyd sleeves since 1968 (sic). The latest, lavish Floyd conception is Shine On, a boxed set of eight CDs and 100-page book for which Thorgerson has written the text.

"I particularly like landscapes, which I use in conjunction with 'mind movies', but to remove them from their normal confines and implanted in a landscape. That way, you refocus the mind. If you wanted to talk about some anomaly of human behaviour, you might take it out of the bedroom and put it in the desert." Or Saunton Sands in North Devon, where Thorgerson turned Dave Gilmour's lyric, "visions of empty beds" from A Momentary Lapse of Reason, into a vision of empty beds - 800 of them, in fact. He admits that his chosen methodology, to visually allude to either a musical mood, album title, theme or a lyric, has always mirrored Floyd's own, open-ended approach. "Our relationship was a very special one. They always treated us very fairly."

By his own admission a bugger to work with - I have a rampant ego and am inclined to be despotic" - Thorgerson lambasts the square, unflexible 12-inch format (since Hipgnosis ceased trading in 1982 he's only sporadically designed sleeves), with special vitriol reserved for musicians - "if they want to design their own sleeve, then they don't need someone like me" - and the record business - "managers don't give a monkey's toss about art ... record companies are bastards, which is one reason why I got out". A temporary shift into video ("the anus of the business)" and the "emotionally, intellectually bankrupt" world of commercials hasn't dulled this wrath.

"The thing is, I've never been that interested in money, which means that you can tell people to fuck off. I had an argument with Mike Oldfield a while back where he presumed to own the artwork. Laughable, really." Still if you don't care much for money, it's easy spending it when it's not yours. "Yes, but what price art, eh? Atom Heart Mother cost a tenner but you could have bought a house with A Momentary Lapse of Reason. "Art is about flights of the imagination, and if art does something to people, then I'm pretty unprincipled when it comes to putting a price on it. You give it, I'll spend it."

The cover of Floyd's 1968 A Saucerful of Secrets. This sleeve, says Thorgerson in the Shine On book that partners their CD boxed set, "is redolent of its times. The superimpositional mix of many items was an attempt to represent the swirling, dreamlike visions of various altered states of conciousness. (Cough, cough)...religious experience, pharmaceutical additives, or Pink Floyd Music.

Parts of the artwork conceived for 1975's Wish You Were Here, whose keynote work, Shine on You Crazy Diamond, was in tribute to lapsed band member Syd Barrett (below). "All the pictures refer to absence in one form or another. The burning man (pictured) is absent metaphorically - too frightened to be present, lest he be burned...Although he was wearing an asbestos suit and an asbestos wig, when we set him alight he was unfortunately facing the wrong way as regards to the wind."

More psyche-warping imagery from the book, which includes detailed histories of the featured albums A Saucerful of Secrets, Meddle, Dark Side of the Moon, Wish You Were Here, Animals, The Wall and A Momentary Lapse of Reason.

The Hipgnosis sleeve for 1973 meisterwerk, Dark Side of the Moon. The design meeting "took about 3 seconds, in so much as the band cast their eyes over everything, looked at each other, said in unison, 'That One,' and left the room."