Tanztheater Wuppertal are her family, her nomadic tribe, 30 men and women who dance, speak, sing and play games. They perform on stages covered in grass, or snow, or mud. They are so devoted to Pina they will throw themselves against walls, wear nappies and smear their faces with lipstick - and that's just the men. They are multinational, as individually flavoured as ordinary people, the opposite of flawless ballet clones. They act with an uncluttered, childlike directness. They are you and me, with our childhood experiences, our adult hopes and fears, our joys and miseries.
Like us, they are all ages - although when the company started 25 years ago they more or less belonged to the same generation. Some early members have retired but rush on stage when Pina beckons them back for a revival, as Malou Airaudo did for the Bausch-Gluck Iphigenia in Tauris at the 1996 Edinburgh Festival. Some continue in the company, such as bulky Jan Minarik who specialises in carrying and cross-dressing, and Dominique Mercy, a sinewy blond Frenchman, edging 50 but still dancing flat-out solos.
The performances of Viktor this week will be the company's first London season since 1982. London needs them more than they need London. Wherever they appear, they are sold out. Ticketless desperadoes stand on pavements - in the June clamminess of Paris, the December snow of Berlin - holding scrawled notices, "one ticket please". A reluctant interviewee, Bausch manages very well without PRs and journalists. Everything you want to know about her, she says, you can see in her work. But occasionally she caves in, or allows her dancers to cave in, especially this time, to please an edgy Sadler's Wells publicity machine.
Dominique Mercy turns out to be charming and informative. I ask how it is that Bausch's performers - trained dancers who do a daily ballet class - don't have the stiff verbal delivery of non-actors.
He explains: "It's because much of the material comes from the dancers. What you see in the pieces, in these small scenes, are the result of questions which Pina has asked us."
Bausch uses these questions or cues to elicit improvisations. "And each dancer responds in a personal way, in keeping with their experiences and imagination." So out of this come many of the Bausch's trademark components: the enchanting visual jokes, such as the makeshift swimming-pool in last year's Masurca Fogo, a plastic sheet held by two men and filled with buckets of water; or the rerunning of intense moments until they become heart-breaking, such as the waif in Tanzabend 11 (1992), who repeatedly drags herself out of the snow, only to be carried back tenderly and cruelly.
If the pieces have the multiplicity of life, it's because they come from just that: from multiple points of view, with Bausch as a funnel distilling them into theatre. She sifts, edits, collates and glues together. "There is a trust between her and us," says Mercy, who in Nelken (1982) plunges his face into a pile of raw sliced onions. "I know that she will not exploit us simply as a form of exhibitionism. It is not the purpose of her work."
He first met Bausch in 1971. "I was immediately dazzled and touched by her person and her choreography," he says. Others recognised her genius early on and Bausch did not struggle through wilderness years. Born 58 years ago, in Solingen, in the Ruhr, she enrolled as a dance student in the Folkwang School in nearby Essen. The distinguished choreographer Kurt Jooss was in charge of the dance department and Bausch learnt classical ballet, modern dance and choreography. At 19 she won a scholarship to New York, where she went to the Juilliard School of Music and worked with another exceptional choreographer, Antony Tudor.
She returned to Essen to assist Jooss with the Folkwangtanzstudio, the school's graduate performing group which he was restarting. She created her first piece for them in 1968, remembered as "very abstract, very dancerly," and soon after became the artistic director, a post she still holds.
Then came the bold invitation from another neighbouring town, Wuppertal, to form a choreographer-led company at their opera house and she started, with Mercy, Jan Minarik and Malou Airaudo among her dancers. The opera house's subscribers, accustomed to conventional ballet, took time to adjust. Her launch piece, Fritz (1974), was already dance theatre, though it had no text. "It was about the fantasies of a boy," Mercy remembers. "And there was a parade of strange guests: a bearded woman, twins, a sick man in a nightgown - that was me." The house was only half-full to start with. "But then people started leaving, slamming the doors behind them."
Her danced versions of Gluck's Iphigenia in Tauris (1974) and Orpheus and Eurydice (1975) scored an immediate success, however, as did her monumental Rite of Spring (1975). After Cafe Muller (1978) she always included words; from Bluebeard (1977) onwards she used improvisation as her creative tool and her work acquired its prismatic, episodic structure.
Detractors claim that this has ossified into formula; yet to me there are clear shifts of theme and emphasis. For example, a Fascist oppression runs through the red carnations of Nelken, which Jan Minarik closes by declaring: "I became a dancer because I did not want to be a soldier." Whereas Danzon (1995) seems to be about ageing and the sadness of this, especially for dancers. It also marks Bausch's performing comeback, in a wrenchingly elegiac solo of arm gestures that resemble a farewell.
So what about Viktor, premiered in 1986? It exemplifies Bausch's desire to preserve the old as well as create the new. It is one of her vast, broad-canvased spectacles, like 1980, which she showed on her last London visit. Viktor was also her first co-production with funding from a foreign city - Rome, in this case - an arrangement she has often repeated since.
"When we do a co-production," says Mercy, "we usually arrive three weeks early in the city to gather sensations and generally open our antennae." These impressions colour the studio improvisations, but the result is an evocation instead of a literal depiction. "Viktor is not about Rome, because what interests Pina is not the city, it is the people living there."
Who is "Viktor"? "He's a ghost; but it will be up to you to decide who or what this ghost is." What else can he say about the themes? He laughs and shakes his head. "When Pina starts work, she doesn't even talk to us about themes." Although she must have certain ideas in the back of her mind, she prefers to keep things fluid, so that the material can develop an organic life of its own. Similarly, to explain a piece before I see it, is to fix my expectations beforehand, closing my mind. "It would be a betrayal to explain Viktor to you," Mercy says.
"What I try is to find the pictures, or the images, that can best express the emotion I want to convey," Bausch once told me. "I am not telling a story in a normal way. Each person in the audience is part or the piece; you bring your own experience, your own fantasy, your own feeling in response to what you see. Everybody comes away with a different impression."
Sadler's Wells, London EC1, tomorrow to Sat (0171-863 8000)