Real diamonds helped Keira Knightley feel elegant in Anna Karenina.
Twelve weeks before he was due to start shooting Anna Karenina, Joe Wright had a brainwave. He's given to these flashes, according to his production designer and long-term collaborator, Sarah Greenwood. ''The thing with Joe is that whatever he says, there's always the nugget of a really good idea in it,'' she says. ''I call it panning for gold: you really have to search out what he's trying to get at.''
But this time the idea arrived like a juggernaut that would pile through the middle of everything they had considered during months of meticulous research, trips around potential locations in snowbound Russia and visits to English country houses that could, at a pinch, be turned into bits of St Petersburg. It was the kind of idea that would probably drive any designer other than Greenwood screaming towards the door.
Wright's concept was revelatory and revolutionary. The conventional costume drama they had all assumed they were making - and which Wright had so successfully done before with his Pride and Prejudice and Atonement adaptations - went out the window. They would set the whole story - palaces, opera theatres, the streets of Moscow, fields of flowers and the rail station where Anna meets her fate - in a derelict theatre.
Everything would swirl and meld into everything else. Furniture would be shifted around and reconfigured before our eyes, and scenery flats would drop in to denote a change of venue. Anna's rakish brother, Oblonsky, would carry out his affairs in the props cupboard, while Anna would take shelter with Vronksy, the dashing young officer played by Aaron Wood-Johnson, with whom she betrays Jude Law's dull and decent Karenin, in blue rooms in the wings.
It was risky, if not crazy - even when it was being shot, the effect of the massed sets waiting to be wheeled on to the stages was so bewildering a seasoned film writer from the London Observer wrote that he could not imagine it working and said Wright seemed excited to the point of madness. ''This could be a disaster, I think to myself,'' he wrote, ''and half-wonder whether I should leave.'' It was a long time before he was able to write that he had seen the result ''and it works beautifully''.
Nobody was really going mad, of course. The idea was fantastic, but the rationale came - as Greenwood says it always must - from the characters and their story. This was a society, Wright reasoned, laced together by artifice. ''One of the things we felt when we were going around locations in Russia was that everything was a facade,'' she says. ''The whole of the way they lived their lives was fake. They spoke French for society, Italian for art, German for philosophy, English for anything sporty or to do with horses - but barely spoke Russian. This kind of lent itself to the idea of doing the work within the theatre.''
Wright had called her at night and for the next week the two locked themselves in a room with a script to work out how the transitions between interiors and exteriors, realistic rooms and fantasy fields of wheat, would work. In the end, Greenwood found she had to whip together 100 sets.
Not all of them were in the studio, either. They were still planning a few weeks in Russia, where they were building the rustic house where Levin, an aristocrat who has chosen to work the land with his own hands (and the story's ''one true soul'', Greenwood says), would live - nestled in the snowdrifts, it was the only set that was correct down to the last Slavic detail.
Then there was the prodigious challenge of the railway station with its rattling steam train - they couldn't afford to build trains in the studio, Greenwood says, so she had her own brainwave and built a stage, complete with proscenium arch, in a shed full of historic engines in Oxford. There was the problem of covering the precious engines with something that looked like ice that could be chipped with a hammer - in the end, she says, the special-effects people spent two weeks encrusting the wheels with wax, a trick used in David Lean's Doctor Zhivago. ''It was a massive undertaking,'' she says. And that left just 99 sets to go.
But Greenwood wasn't overwhelmed - she was relieved. The great fear had been that this Anna Karenina, despite its rich Tom Stoppard script, would be a bit dreary. Travelling around Russia with a local scout, they were shown one location after another where, they were told, ''this is where we always shoot Anna Karenina''.
The secretaries of the English country houses they visited would enthuse about the prospect of Keira Knightley - another of Wright's regular collaborators, whom he had cast as a willowy Anna - swishing through their period rooms. Meanwhile, their budget was tightening. ''The whole thing was becoming a real patchwork and very unsatisfying,'' Greenwood recalls. ''It was so stimulating when this idea came in; it reinvigorated all of us. We all went 'Wow', you know.''
One person saying ''Wow'' with some trepidation was Jacqueline Durran, the costume designer. She might have known what to expect - this was her fifth film with Wright. She had known from the outset he did not want replica outfits from the 1870s or real military uniforms, that the costumes should suggest the period but evoke ideas of luxury and elegance that audiences would recognise. In addition, Wright gave her a key word: silhouette. ''He always has a picture of what direction he's thinking of, a touchstone. With Pride and Prejudice, it was 'provincial','' she says. ''He's an extraordinarily visual director - his interest in costume comes from puppets.'' Wright's parents ran the Little Angel Theatre, a children's puppet venue in London. ''So he has always been conscious of the possibilities of costumes and how costumes move.''
By the time Wright had his big idea, Durran had produced a range of designs combining crinolines with the nipped-waist jackets, princess sleeves and cowl necks of 1950s couture. ''I used asymmetry - an asymmetric fastening would never have existed in the 1870s. And there is a kind of swoop of satin around Keira's neck in one dress which is a very '50s thing, while the skirt shapes stayed more or less 1870s. It was all about a way of looking at clothes in which the silhouette dominates.''
Colour was crucial - in one of the most impressive scenes, everyone is wearing pure white - because the emphasis on line meant Durran could not embellish Knightley's frocks with a lot of lace or trimmings. ''You're back to the bare bones. So you start asking, 'How do I beautify that image?' So you start playing with colours.''
At that stage, she imagined the costumes among the brocades and polished woods of a period piece. ''When we changed direction, I couldn't imagine the costumes for a while because I couldn't imagine their settings. One wouldn't have thought the two things were interlinked, one would have thought, 'Oh, just get on with it.' The whole thing was quite tricky for a few weeks. I would ask Sarah - she's the greatest collaborator of all - where are they going to be? And she would say 'In the props store,' and I couldn't think what that meant.''
Of course, Durran did get on with it. It was a matter of some urgency, since even the crowd required 200 individually made costumes. The mass effect, emphasised by the way the extras sometimes freeze in position as the principals wrangle in the foreground, has the zesty impact of a musical. Durran's long-standing creative partnership with Wright - which had already brought her two Oscar nominations - meant she felt free to try ostensibly wacky ideas, such as making Knightley a crinoline dress out of denim. Like her director, with whom she, too, has worked three times, Knightley is fervently interested in costume - so much so, Durran says, that she sometimes sketches her own counter-designs.
''Keira liked the idea that her clothes would often be crumpled; that expressed something to her about Anna and her carefree nature.'' Each day Knightley was invited to choose from a tray of real diamonds, lent by Chanel and worth a cool $2 million. ''I think using real diamonds was a great thing for emphasising the privilege of their lives,'' Durran says. ''The necklace she wears twice, at the ball and the opera, captures the light in a way that is amazing and that you wouldn't get from paste, and I think it plays into the way you work with an actress.
''She really was in this privileged position of having millions of dollars' worth of diamonds to choose from and I think that's part of the way Anna would have been. It wasn't necessary for Keira to feel she was stepping back into the 1870s. What she was aiming to feel was that she was the most elegant person. Accuracy wasn't of prime importance - opulence was.''
Durran and Greenwood - along with set decorator Katie Spencer - have been nominated for Oscars in their fields. This is a film all about appearances, about surfaces, illusions and delusions. A vision, in other words - not one that will necessarily please literary fans of Leo Tolstoy's massive tome about passion and civilisation, but an extraordinary thing to see.
Seamus McGarvey, the marvellous Irish cinematographer whose CV reads like a catalogue of recent British film and who is also nominated for an Oscar, says he relished the work: all the tracking shots and the effects he had to make in-camera because digital work would detract from the solidity of the sets. ''Working with Joe,'' he says, ''you're always presented with difficult challenges - he really pushes every department to do their very best. He won't settle for average.''
In fact, it really does make you say ''Wow''.
■ Anna Karenina opens on February 14.