Cedric Price is that rare thing: an architect who is far more interested in the social and practical impact of his buildings than in producing monuments that he can point to with the words, "I did that." He is one of Britain's most influential living architects, yet he has relatively few buildings standing, and it is his ideas that fire imaginations. His best-known completed project is the revolutionary lightweight aviary at London Zoo, which he designed with Lord Snowdon. And he even wants to see the back of that. "The whole business of looking at caged birds is now pretty unacceptable," he says.
He turns down clients if he doesn't think there is a good enough reason for taking on the commission, and has suggested that the man hoping to transform his life with a new house might be better off getting a divorce.
"Timing is always, always the most important thing with architecture," explains Cedric Price, a genial 64-year-old with a fondness for white-collared shirts and good cigars. "Only in this century have we failed to realise this. In the 17th century, the machine for living in was used and re-used, rebuilt and re-styled constantly. Things were left to ruin, entrances were changed. It hasn't always been the case that the client is satisfied with what he's been given and will always want that."
Price's insistence that buildings must be open to flexibility and movement has deterred many potential clients. "Constructed, calculated doubt is part of our job, but most clients don't want to take on uncertainty and chance. Most modern buildings are, either symbolically or for more villainous reasons, designed to give a sense of permanency and respectability. The Lloyd's Building is a case in point - it was an antidote to risk in a visual form. The organisation collapsed about a year after the building was completed."
Even the Pompidou Centre in Paris, which was partly inspired by Price's work and whose stack of clear floors is designed to be adapted according to usage, falls far short of the kind of structural freedom he envisages. "The French government is quite different from the sort of clients who take me on - they're not too keen on any kind of flexibility. In France they want an object, a gem. I don't do gems. Or prisons, or cathedrals."
Insecure clients would be thrown into a panic by some of Price's unrealised projects. A great believer in the non-building, he suggested turning a disused railway line in the depressed area of Staffordshire into a mobile university in his 1966 Potteries Thinkbelt project.
Meanwhile, his masterpiece that never was, the Fun Palace, would probably have Lloyd's trustees throwing themselves from the top floor of Richard Rogers's most famous building. Conceived in the mid-1960s in collaboration with the theatre producer Joan Littlewood, the Fun Palace was a futurist, socialist dream-world, a "university of the streets" with cinema screens and theatre performances. The Labour-supporting Price saw it as a way of combining education and entertainment for all classes without the condescension of "piping Beethoven down the pits", as he puts it. It was to be built in London's Dock-lands, and was designed as a series of movable parts that could be lifted by crane, dismantled when necessary, and even eaten when the masses got peckish.
"Yehudi Menuhin was one of the trustees," Price recalls, "and he was very keen on it because we promised him that there would be semi-nude mud wrestling. But the time for it passed, with greater unemployment in the area and the advent of colour television meaning that more people stayed indoors. If it got built now, someone like the Twentieth Century Society would stick a plaque on it the moment it was no longer relevant."
As Price knows all too well, odder things have happened. He is now at the centre of a row about one of his designs from the early 1970s - the Interchange Studios in Camden, a loose arrangement of Portakabins and enclosures around a structural frame, currently used as a community arts centre. It was one of the inspirations for the Pompidou Centre, but its creator wants to see it torn down.
"It doesn't interest me to have it saved," says Price, who has produced a manual detailing how the building should be dismantled. "It was made on the condition that it had a 20-year life span, and it's beginning to look like it has run over its time." Much to his dismay, the centre has been earmarked by English Heritage and the Twentieth Century Society as a hugely influential part of architectural history that must be preserved.
Price's vision has been driven by ideals, by the idea that architecture must "enable people to think the unthinkable". Most of the profession, he argues, is incapable of responding to the needs of our time, and it is far more important to address social issues than to immortalise personal dreams in bricks and mortar.
An example of this way of thinking is the Fun Palace Mark II, which he insists is completely in keeping with the philosophy behind Mark I. "It wasn't a building at all - it was a phone card. As long as you called someone to spread good news or tell a joke, it would give you extra credit. But if you told them bad news or threatened them, it would wipe itself clean. It's entirely possible, as well: computers can now read intonations in people's voices that give away their moods. Even chimpanzees might find it useful."
Price's latest British proposal is also driven by a political issue: the concept of private property. The Magnet project is a series of mobile structures designed to transform and revolutionise sites around London.
A walkway snaking through the trees in Regent's Park would allow the public to see into London Zoo and have a peek at the animals for free; a platform at Tottenham Court Road would have giant hydraulic arms giving people the chance to spy on office workers hiding in their fourth-floor offices; a hover-pier on the Thames at Burgess Park in south-east London would act as a mobile platform, complete with a reasonably priced fruit and veg. stall; and a mobile bridge across the North Circular would make the air space above roads and the derelict land beyond open to all - redefining boundaries, which is, after all, the essence of all Price's work.
Price is like a child-genius, an innocent who is truly principled and yet capable of the most far-reaching thought processes. Unsurprisingly, he doesn't rate architecture as particularly important.
"There's a wonderful book by an architect called Things Which Are Seen, in which Tristram Edwards lists the arts in terms of importance. At the top is the art of manners. Then comes the art of language, then various things like flower arranging and music, until you reach architecture at number 11." His designs are accused of being deliberately anti-aesthetic (to which he responds: "I always have to look it up in the dictionary when people say that. Then I say, I'm sure aesthetics are very good for you") and wilfully perverse, but what they really seem to demonstrate is a social conscience combined with a delight in the unknown.
But how successful has he been at creating a building that is flexible and open to change?
Of the Interchange Studios, he now says: "The best thing that happened was when Whitbread breweries bought part of the building and turned it into a pub with a mock-Tudor interior. It took me eight months to build it, and Whitbread took a lump of it and knocked up a pub over the weekend. I was very pleased about that."
