Thankfully, the patient was not seriously ill. However, my companion thought that a few benign collapses were a rather appropriate audience response to the extremes of Sankai Juku. This company has become internationally famous as the practitioner of the startling theatre form called Ankoka Butoh, or Dance of Darkness, invented by the Japanese avant garde in the early Sixties. Originators such as Kazuo Ohno and Hijikata built upon Japanese theatrical traditions as a reaction against the post-war Americanisation of their country; they incorporate an anguished grotesqueness that seems to turn the human soul inside out and which some commentators have seen as rooted in Japan's atomic ashes. But they also grafted on some of the precepts of Western modern dance - especially the German expressionism of Mary Wigman - in which they had themselves been trained.
Ushio Amagatsu belongs to the second generation of Butoh, founding Sankai Juku in 1975. He too trained in Western modern dance, and in ballet, and upholds the importance of a uniquely Japanese culture - "culture has meaning precisely because it differs from other cultures," he says. But his version - he composes the choreography and designs the settings - is visually glossier and more other-worldly than the reputed visceral sensationalism of early Butoh.
Watching the on-the-edge deliberation of Sankai Juku, I pondered with some alarm just how excessive early Butoh was. The men themselves look so weird, a colony of Star Trek aliens or primitive clay figures, moulded by a craftsman in a hurry. Then there are the images, created through extraordinary movement and a starkly exquisite symbolism, images that evoke both philosophical profundity and mysterious ritual, images that hover ambiguously between beauty and horror, between pain and ecstasy. In one piece they showed in London, a man danced with a live peacock, abruptly seizing it as though about to strangle it. At the 1982 Edinburgh Festival, the company lowered themselves upside down from the Lothian Building - a publicity stunt that plunged into terminal tragedy in Seattle four years later when one man's rope broke.
I talked to Amagatsu in a Paris cafe an hour after the performance. The Sankai Juku stage-look is so scary, it was a relief to see a dapper, middle-aged man arrive. He wore a cap to keep his shaven head warm and was sufficiently in tune with French living to order a glass of champagne.
Although the name Sankai Juku - meaning "Workshop by the Sea and Mountains" - refers to their original creative base in Japan, France has since welcomed the company in a big way, providing rehearsal facilities and part of its financing. The Paris show, Hibiki, was new; but for its Sadler's Wells visit, its first to London since 1991, it brings a 1988 piece, Shijima. (You may not find it illuminating to know that this translates as "The Darkness Calms Down in Space".) Shijima has been described as a quasi- religious ceremony, a slow requiem of gestures, the stage walled with white crumpled parchment on which are imprinted human silhouettes. Shijima, says Amagatsu, forms a diptych with another piece, Unetsu, which was performed when Sankai Juku was last in London. "Shijima is quietness after Unetsu," he states. "We can say that if Unetsu is wet, Shijima is dry."
It is impossible to know whether the interpreter's laboured English is responsible for this brazen verbal minimalism or whether Amagatsu's thinking simply operates that way, matching the oblique conceptualism of his stage work. But he has a twinkle in his eye, and is game to elaborate when pressed. Unetsu was billed in London as representing that part of life's journey between the womb and birth. Its decor included standing eggs, a swinging pendulum, water and sand. "The water," Amagatsu says, "symbolises the origin of life; the sand is the last thing that life goes towards". Perhaps, then, Shijima is more about life's last thing, the floor covered in a thick layer of sand, the dancers' robes caked with it, as if people are mobile extensions of the ground. I sense, though, that like many choreographers he doesn't like to delve into too many explanations of significance, preferring audiences to find their own reference points.
What is Butoh for him? "For me it is a dialogue with gravity." And? And? "In Western dance, some people make a thing about being against gravity. But for me, my dance is in harmony with gravity."
That strikes me as being in keeping with the Western Graham technique he has studied, as is the importance of breath he also mentions. He tries to explain the principle behind his emphasis on slowness with a visual analogy, demonstrating with his hands the positioning of three far-apart dancers, the two outside ones revolving around the middle one like planets. "The one in the middle circles on the spot very slowly, but the other two have to travel very fast to make the same number of circles in the same time." This represents a metaphor for the opposition of body and consciousness: a dense physical centre that is almost static, but with thought processes that have the scope - and speed - of light.
I struggle to grasp how this relates to a performance on stage. Have I understood correctly? That the dancer's mind is limitlessly active, concentrated on subtle, barely perceptible shifts of dynamic and texture. Either way, this internal approach is echoed in the company's daily class, based on his own method. "We don't use mirrors, because I don't like the dancers to change their movement when they see themselves." He wants the movement to come from within. He repeats: "My way of doing is not speed or shape but the consciousness of the dancer."
He says his company is all-male because it evolved out of his dislike of mirrors. "When I started I held a one-year workshop for 30 dancers, male and female, but because I held my sessions without sound or mirrors, the women gave up." It is meant as a smiling answer, but it also strikes me as disingenuous, since much of his theatre depends on the absence of sexual difference. His performers are androgynous, sometimes dressed as men, sometimes as women; they are everybody, non-individuals, moving in unison. This ties in with his explanation that their shaved and whitened skin is not a shock tactic, but a way of simplifying them to their human essence. "I want to achieve a balance between difference and sameness," he says. By which he means that although he is committed to a distinctively Japanese style of performance, he is equally preoccupied with dance's universality, its potential to be understood everywhere.
Sadler's Wells, 18-22 January, 8pm (0171-278 8916)Reuse content