The heretic master of frozen motion

He stood quietly dressed and slightly bemused, under Rubens' Apotheosis of James I in the high-ceilinged splendour of Inigo Jones' Banqueting House in Whitehall. Two skinny microphone stalks framed his jet-lagged face like quote marks. He fiddled with the laser-pointer and his opening remarks were tentative. "Inigo Jones and Rubens. It's too bad to muck it up with these screens. So, I'd like to show you some recent work. On the left-hand screen... uh... what you see... uh, no, that's not right..."

He stood quietly dressed and slightly bemused, under Rubens' Apotheosis of James I in the high-ceilinged splendour of Inigo Jones' Banqueting House in Whitehall. Two skinny microphone stalks framed his jet-lagged face like quote marks. He fiddled with the laser-pointer and his opening remarks were tentative. "Inigo Jones and Rubens. It's too bad to muck it up with these screens. So, I'd like to show you some recent work. On the left-hand screen... uh... what you see... uh, no, that's not right..."

The 71-year-old, whose work is described by the architectural commentator Charles Jencks as being imbued with the spirit of fog, took the glitzy audience through a self-deprecating tour of his latest work. There were pauses, softly-spoken musings, and even a moment or two of profound and hastily concealed emotion. Was this any way for one of architecture's great creative forces to behave? Could this really be the profession's most sensually fissile entity - a Pope and heretic rolled into one - whose cancer care unit in Dundee will be his first work in Britain?

Six hours earlier, Frank Gehry had walked unassumingly into the high-rez office of Marco Goldschmied, president of the Royal Institute of British Architects. Gehry noticed that the male journalists waiting for him were wearing ties. "Oh, I guess I'm not wearing a tie," he said doubtfully. Goldschmied, in dark blue T-shirt and super-cool designer ragamuffin duds, beamed.

It was the simplest and most unselfconsciously disarming of moments. There were to be many more. The genius of this most unlikely of architectural radicals flows from his search for personal rather than intellectual fermentations; that, and a rare kind of self-effacement, set into the folds and fragments of communally creative processes that are as securely rooted in fine art as in architecture. Gehry is considerably happier talking about Bellini's Madonna and Child or fish-shapes than, for example, Norman Foster's Millennium Bridge.

But it's highly unlikely that any of us would have been in that room if it hadn't been for Alvar Aalto and a lecture he gave in Toronto more than half a century ago. In the audience was a 16-year-old, born Frank Goldberg. "A wonderful man from Finland showed a chair," Gehry recalls. "I loved him. I loved the lecture."

A decade later, after walking out of a town planning post-graduate course at Harvard, there was another vividly crucial moment. This time Gehry was working as a truck driver - but mixed with "creatives" - the spark-gap was lit up by the Californian modernist architect Raphael Soriano. It wasn't so much Soriano's architecture that attracted the young man, but the fact that he was built like a boxer and went round his studio, shouting: "Do this! Change that!"

Gehry's early attraction to architects and artists who knew how to make things happen has since matured into a core belief that the only way ahead for innovative architecture is for architects, rather than contractors, to be accountable for finely calculated risk-taking; to know exactly what their materials can and can't do; to become, again, master builders. Only then, he believes, can more architecture provoke engaged and creative reactions.

He is chary of "perfected" architecture: "You try to build your building to the best of your artistic and intellectual abilities," he says. "But you also try to deal with the context - and in that sense you're dealing with chaos. Or you can ignore it and build a 19th-century enclave and say chaos doesn't exist."

Gehry has been spotted reading philosophical texts on folding theory by Derrida and Deleuze, but his response to Carl Andre's notorious 155-brick installation in New York in 1966 is a better guide to his mantra of blurred intuition. "Yeah," he recalls. "I bought it. The bricks made me think about the experience of working with materials."

For this particular master builder, the road has been tortuous and his Bilbao triumph must be seen in perspective. Here is an architect ("and the other thing is, I'm not rich!") whose studio's quantum jump into the big time - his staff number 130 today - only really took off in the 1990s. At the end of the 1980s, his Santa Monica home-cum-atelier was almost absurdly low-tech: a word processor and another computer that did the accounts.

At that time, the flowing, neo-baroque forms that he was working on were built up with blocks, to develop rough layouts and volumes, and then models were cobbled together with junk materials. "I sit and I watch and I move things," is how he puts it. "I move a wall, I move a piece of paper. I move something and I look at it - and it evolves."

Today, that evolution is refined by software originally designed by Dassault for aerospace configurations. The complex flows and contortions of Gehry's studio models are, in effect, scanned with utter precision. This allows highly accurate engineering and materials calculations; and a great deal of time and money is saved. The Bilbao museum, and its paper-thin titanium skin, came in on time and on budget.

The only thing he designed completely on computer shattered him. He created the form of the so-called "horse's head" ("it isn't a horse's head and I don't know what it is!") conference room in the DG Bank headquarters in Berlin. "I hated it. I used to scream. I'd run out of the room. I couldn't stand it for more than three minutes. And I wasn't manipulating the computer, my assistant was. I was saying, move it up a little here, move it up a little there.

"The image on the computer was such a dried-out version of the image I had in my head that I just couldn't... I had to retain the image in my head while I was looking at this, uh, thing. It was excruciating. It was like hanging on to a 1,000lb weight and if I dropped it, it would land on my toe. Wow! It's difficult. But the kids do go straight on to the computer, but they haven't got the experience in building, and the most difficult thing for any architect or creator is to get your idea through all of the layers of folks that have to touch it before it's finished."

Gehry has always minimised this aspect by working only with clients with whom he has formed a personal bond. For example, New York has been robbed of a stunning skyscraper - Murano vase meets Marilyn Monroe's hips and thighs - because Gehry found it impossible to get up close and personal with his clients, The New York Times.

This isn't evidence of concealed arrogance. The Microsoft billionaire Paul Allen approved Gehry's early concepts for Seattle's "melted guitar" Experience Music Project, but was not involved in further development of the plans. When Gehry presented the finished scheme, the client didn't like it. "I didn't get petulant and say, Mr Allen, take it or leave it, which I could have done, and I think he would have accepted it. But I was so empathetic to his feeling that... it was almost like a betrayal, like I'd set something in the past and then where it went was a betrayal of that past. And I thought, I can't do that to this guy."

And so it is just as Charles Jencks put it at the close of the Riba Gold Medal ceremony. "You've shown us," he said, "how to stay hot and fogged, setting a standard of decency and greatness."

Riba may have blessed Frank; but the Pope-heretic of Santa Monica blessed the audience on Wednesday night - and that seems a bigger deal. So praise Aalto, hail the inquisitive 16-year-old Frank Goldberg and do something Bilbaoish with the foil on the champers. The ghosts of London town's medieval master-builders must have watched his apotheosis with much satisfaction.