Vicky and Al's Big Adventure

As the V&A finalises plans for its avant-garde new Boilerhouse extension, Jay Merrick follows its creator, Daniel Libeskind, from London to Berlin to probe the making of a modern masterpiece

When the Victoria & Albert Museum's Boilerhouse extension - a controversial, hi-tech structure known as the Spiral - enters its final planning stage with the Royal Borough of Kensington and Chelsea this week, key questions will centre on the ideas of its designer, Daniel Libeskind, a man who has been described as architecture's Pol Pot.

The Spiral is certainly extraordinary. Its seven-storey design features space-age materials, complexity theory and a frameless construction, and is poised to electrify South Kensington with the shock of the new. Thousands who shop at Mr Fayed's spiffy emporium down the road will regard it as an affront to mediocrity.

But would they be right to do so? They might, instead, ask what makes Libeskind tick. How does the man's mind work? What has the V&A tapped into? The questions ripple outwards to Berlin and yield a fascinating exposure of the deepest seams of the processes of modern architecture.

Berlin's Lindenstrasse is virtually deserted. It's a sunny Saturday afternoon; youngsters are languidly playing opposite the city's Stadt Museum. The decaying neo-classical facade is screened by a fence plastered with posters advertising death metal bands, New Model Army's Strange Brotherhood tour and "Burger King - Walt den Whopper!"

A few yards south of the museum, and looming above it like a hugely fractured ingot, is a stunningly mysterious zinc-sheathed structure born from the ashes of an incinerated generation, a building whose tortured genesis caused an intellectual and emotional ferment in Berlin that lasted the best part of a decade.

The vituperative row can be said to have oscillated between two starkly contrasting visions in the Jewish thinker Walter Benjamin's fragmentary musings, One Way Street. On the one hand, the idea that memory can be a "horrible cabinet of curiosities", and on the other, his exquisite remark that "separation penetrates the disappearing person like a pigment and steeps him in gentle radiance".

That controversial ingot is Berlin's Jewish Museum, due to open this summer. It earned Daniel Libeskind praise and vilification in equal measure - and the put-downs were, at times, monumental. The 52-year-old Polish- born polymath has, for example, been branded as a destroyer of Berlin. Yet the "destroyer" seems to have an army of unlikely followers. The Jewish Museum has unexpectedly become a leading attraction. Thousands of punters ("They're not art critics, they're just normal people," said a beaming Libeskind) have been shown through its strangely intersecting galleries and apparently inexplicable concrete voids.

Mr Pot, he is not. Compact, dressed in the international architect's regulation matt black, hands always on the move, discourse and asides flying out like doves from a magician's sleeve, he is simply the personification of his architecture. Attracted to the mystical and to forces of intuition, Libeskind remains utterly dominated by the need to produce works that are perfect expressions of intent and function.

Beyond the tatty hoardings in the Lindenstrasse, the sunlight sheers off the building's strangely massed facades and angled windows. Its visual signals seem not so much mixed as from an unknown place. Initially, the Jewish Museum is beyond description; it demonstrates no known style.

Walking up the dark, oddly angled underground ramp one is confronted with two corridors angling away in an ambiguous V - which way ought one to go? - and the first of the museum's seven voids. And, as with the exterior, there is an unsettling sense of the ungraspable in the oddly angled and linked spaces in black, grey or white. Nothing is normal, yet there is an overwhelming sense of a precise intent. Something is there, waiting to be found ... or lost.

And then, Libeskind's revelation, the touchstone for what may be the only museum in the world that is itself Exhibit A. He selected 1,050 Jews who had formed the weft of Berlin's pre-war tapestry of arts and sciences - Jews who invented the

Goethe Society, Jews who considered themselves so utterly German that their families' tombstones in the Weisensee cemetery carried gothic rather than Hebrew script. Libeskind found out where they had lived and plotted the lines from their homes so they ran through the museum site to create an "irrational matrix in the form of a series of squared triangles yielding reference to the compressed and distorted star, the yellow star that was so frequently worn on this very site".

He used this extraordinary web of intersections to plot not only the museum's horizontal planes, but its vertical and angled ones, too. Virtually every line, every window, every dimension and space is vectored into those 1,050 Jews who perished or were exiled.

And so Berlin's Jewish Museum is a kind of rune, a repository for what Libeskind calls "the things that never came to fruition, the traces that were never born in this city". In some of the spaces, particularly the voids, there is a leaden sense of the capture of time that stopped in the mid-1930s when Jews "believed themselves to be carriers of the German idea of culture. They created the idea of modernity. And it was fatal".

There are other complex ideas immured in the Jewish Museum: the relationship between what cannot be represented in architectural space, and the architecture itself; what Libeskind described as "the invisible city that's all around it, the city that's still there and everybody comes and looks for it", and finally, Schoenberg's uncompleted opera in which the third act, written after his exile, had a libretto but no music.

"I fought for it because I do think the citizens, the taxpayers, understand it. Had it been just a neutral box it would never have got built, that's for sure. There would have been no reason to do it."

And it was this same intellectual rigor and passion that carried the day for Libeskind's V&A Spiral design, seeing off aesthetically mannerly entries from gilt-edged competition including Sir Norman Foster.

When the Spiral's design was first publicised it received predictable condemnation. Architect Ian Simpson said: "It's not a modern building, but a piece of sculpture that looks dated already." Another, Ben Derbyshire, said the design filled him "with dread that we can seriously consider such a building in our midst".

Of course, the V&A's history is littered with brouhahas, starting in 1856 when the Department of Practical Art built the South Kensington Museum - two rather lumpen prefabricated iron structures which looked like the barrels of huge steam engines and were promptly dubbed the Brompton Boilers.

The sledging cut no ice with Henry Cole, the museum's brilliant eminence grise who understood something more important: that even in the mid-19th century, arts and craft had to compete. It needed a modern approach. His decision to install gas jets in a later building was typical: he wanted to attract visitors of all classes in the evening; the museum, he said, was to be "a powerful antidote to the gin palace".

The V&A Spiral may appear wild - one sympathetic critic described it as "an explosion in a cardboard box factory" - but its creator is no feral iconoclast or closet sculptor. This can be demonstrated by examining the considerations that drove the design of the Spiral and rolled the opening credits on what has become Vicky and Al's Big Adventure.

According to the V&A's major projects director, Gwyn Miles, Libeskind got the nod because his building made the hugely avant garde statement required - and because it met every practical demand of the brief in detail. "We know the Spiral will work," said Ms Miles. "It's spot on. He listened to what we said better than the other architects."

That the V&A could even consider a new building as radical as the Spiral has much to do with a "conscious decision we made about 15 years ago to go back to our roots and make sure that we did collect the contemporary".

Since then half the V&A's annual pounds 800,000 purchase grant has been spent on contemporary material. Just the one problem, though: it has no suitable galleries to do them justice. The museum's current 20th Century Room, for example, is appallingly fusty. There are some treasures but they moulder in poky cases under low-budget film noir lighting.

If the great and good wave the Spiral through, they will have cattle- prodded South Kensington's architectural heritage into a kind of fourth dimension. The variable geometry of the Spiral, its three-metre-wide exterior ceramic tiling and look-no-hands engineering calculations by Ove Arup that have used Nasa computer technology, is poised to create a pounds 75m craft object that will seem to have been beamed in from the late 21st century.

The design was developed after a careful study of the relationship between Cromwell Road and the roofscape - what pedestrians will see, on one hand, and the building's internal functions. "Its form is a spiral, but not like any spiral that's ever been built," Libeskind explains, "because there's not a centre or a single trajectory. It doesn't have an apex." The spiral concept reflected the way existing galleries - built at different times by different architects - were connected.

"It's a sort of vertical slice through time and you can find everything side by side - Raphael cartoons, Islamic art, fashion - competing with Europe and the world. The Spiral is a retrieval of the V&A's original idea. It's not about, `where do I find the Queen's Jewels?'.''

The Spiral is for keeps. It has to last at least 120 years - an unprecedented stipulation. "The client was actually asking for something for another time," said Libeskind, "a craft and a culture for eternity, so to speak. One has to reinvent and retrieve technology. So it's not because I'm searching for complexity or I'm masochistic and trying to find difficult things to do - it's the challenge of the V&A's programme."

At our first meeting, over dinner in the Soho House club, Libeskind appeared blissfully unaware of the wannabees, made-its and cheroot-smoking femme fatales that populated the dining room. Instead, he rattled on about details: how hard it was to design the windows, the technical problems of maintaining the facade and "its beauty over a long period of time".

Thus, there is no obvious shred of the showman in Libeskind's make-up - or if there is, it is the technically elegant bravado of the concert pianist he once was. "It's hard," he insisted, "because architecture ... what is it? It's a few drawings, it's models. It's not the real thing. The real thing is elsewhere. It's in space. It's in time. It's in the effort to construct it, to make it real. And that's what I seek to communicate."

For Libeskind the Spiral is not just a striking design, it's a kind of architectural reality-check. "It's always, finally, that element of surprise, the element that cannot be simulated in any simple way ... What can be simulated is not real - only that which cannot be simulated, that which is truly in space, is architecture."

Berlin's Jewish Museum, which will contain a bare minimum of exhibits, is about the past and loss; the V&A's Spiral, which will be packed with all that is extraordinary in modern design, is about finding the future. It seems that Libeskind, in deference to Schoenberg, has produced the equivalent of two operatic third acts: one thronged with silence, the other singing to the music of a new avant garde.