Michael Clark, Sadler's Wells, London<br></br>Dance Umbrella's 25th Birthday Gala, Sadler's Wells, London

How to divide an audience straight down the middle

Twenty-five years ago, a little festival calling itself Dance Umbrella crept into being. Its opening night - a modest mixed bill at London's Riverside Studios - presented a handful of practitioners in strange new territory. They called it contemporary dance, but no one knew quite what to make of it, and during one item in which a man edged very slowly round the floor on his bottom, some of the audience started to heckle. Then another faction argued back. It was hardly a riot of Rite of Spring proportions, but it set the seal on the discursory future of British contemporary dance. A quarter of a century later that same festival is vastly richer in diversity and scope. Many of its early discoveries are international stars. But it's still offering up challenges and conundrums, still dividing audiences clean down the middle.

Love him or loathe him, Michael Clark has occupied pole position for much of the past two decades and is British dance's true iconoclast. Never mind the patchy productivity and a tendency to repeat himself: there is simply no one like him. And that was the overwhelming feeling as he unveiled his latest collection of pieces to a packed Sadler's Wells, including several hundred brave souls who thought it worth £5 to stand (part of the successful Jerwood Proms initiative).

Few expected to find anything really new. You run a mental checklist of the features as they happen. There are the silly jokes: a corps de ballet dancing with brown paper bags over their heads. There are the gestural references to disco. There are the usual ear-bashings of heavy metal, this time from Seventies "Krautrock" and PJ Harvey. And there are the teasingly brief - briefer than ever - appearances by Clark himself, who nevertheless manages to squeeze maximum charisma from the minimum of exertion.

At 41 he clearly no longer trusts his body to deliver what he wants, so the trademark goose-stepping grands battements and teetering balances are out. The movement in his solos is scaled-down and sober. Yet even when you suspect Clark might be indulging in some private blue joke (one floor-bound sequence is clearly about penetrative sex), his concentrated cool control makes mesmerising viewing.

The energetic stuff goes to his younger company members who are at their best in the terrific punk blast of Submishmash, to music by the Sex Pistols. Almost 20 years on from his first experiments, it's still thrilling to observe how Clark meshes the raw thrust of popular culture with the refined exactitude of ballet. And this quality survives all the gimmicks he throws at it.

In Oh My Goddess he dresses the company men in short pink frocks. Why? I guess "Why not?" would be his answer. For whereas Pina Bausch and others have used cross-dressing to make a political point, Clark seems to do it just for the hell of it. Subversion is in his blood to such an extent that even pointed feet and turn-out end up looking fetishistic. But when the steps are delivered with this level of energy, at this level of precision (and barefoot, what's more), the performance justifies everything.

Yet it was the more static Satie Studs - a set of short pieces set to the music of Eric Satie - that made the evening's highlight, not least for the theatrical coup of four concert-size pianos and their pianists strung ominously across the back of the stage like a fleet of black limos. Clark is still capable of the grand gesture. And having them all play different Satie pieces simultaneously (Clark's idea) was a weird and glorious experience. The effect was the aural equivalent of a Gothic cathedral, arch upon arch upon echoing arch - and the accumulating dance steps figured likewise.

The sheer diversity of what counts as contemporary dance these days was never more clearly illustrated than in Dance Umbrella's 25th Birthday Gala. You thought it was about going barefoot? Two of the items were on pointe. You thought it was all about youth? Two of the big-gun performers were well over 50. You thought it had to be serious? Dear me, no.

The organisers had tried to include a bit of everything - to present a kind of Who's Who from both sides of the Atlantic, though if they'd given a slot to every choreographer who owes their UK career to Umbrella we'd have been there all night. A lithe 66-year-old Trisha Brown delivered an enigmatic solo with her back to the audience. Bill T Jones (an HIV survivor for so long now that people forget to marvel at it) showed his magnificent physique to witty effect in a pec-flexing number. And Mark Morris, whose girth increases by the year, showed that even fat people can hack it in an exquisite round-the-world tour of dance styles that took in Javanese arm-rippling and Spanish castanets.

The British contingent was led by Richard Alston, whose Dangerous Liaisons (1985) was performed by Scottish Ballet - proof of the way in which dance genres have cross-fertilised in recent years. Now cyber-heads like Wayne MacGregor will happily make a duet (2 Human) for the Estonian ballet stars Thomas Edur and Agnes Oaks, and for all her scaggy punk get up, it's a classical tour de force.

Coming from the opposite direction was Matthew Bourne's Spitfire (1988), a skit on male vanity in which a bunch of male underwear models (led by Adam Cooper) pose and pout in beefcake groupings that mimic famous moments in Romantic ballet. But the vintage piece that tickled me most was all new to me. The American Charles Moulton's Nine Person Precision Ball Passing is exactly that: nine girls in school sports kit, arrayed for a team photo, pass coloured balls to each other with a dexterity and timing that makes not just fascinating 2-D patterns, but delicious comedy. The variety of dance's vital energies knows no bounds.

jenny.gilbert@independent.co.uk

The Dance Umbrella season continues at venues throughout London until 8 November. Programme details from www.danceumbrella.co.uk