George Piper Dances, Sadler's Wells, London

Bath time with the Ballet Boyz

"Shall we do that bit again?" cuts in a woman's voice. "You know, that bit where I do this and you hold me here?" It's what you'd expect at a rehearsal. But this comes 10 minutes into an opening night at Sadler's Wells, midway through Approximate Sonata, I, V, a duet by Europe's leading ballet innovator William Forsythe. In a trice the spell, painstakingly worked by the choreography, is broken. The two prowling protagonists no longer seem like visitors from Planet Zog. They are just ordinary people doing a job.

It's typical of Forsythe to pull the rug from under his own theatricality, but it also happens to suit the tenor of the evening as a whole. Because to be in a theatre in the presence of TV's Ballet Boyz - Michael Nunn and William Trevitt - is an invitation to peer into the dancers' world. The pair are now in their third year as George Piper Dances, and the format has become quite familiar. Jocular, casually shot video of the company in rehearsal and on the road intercuts high-spec live performance of contemporary ballet. Even when you've seen it before, the effect is lively and illuminating.

What's clever about the GPD format is that it doesn't patronise. We see Trevitt chatting to camera from his hotel bath in Frankfurt describing an encounter with Forsythe; we see the glamorous Oxana Panchenko try a move and topple over. The point is not to show the performers as goofs, but to strip away the mystique that can make new work seem remote. And it works.

Another familiar feature of the GPD experience is their knack for tracking down good material. Big ballet companies wait years for a work from Forsythe, but GPD jumped the queue by doorstepping him in Germany. Approximate Sonata - not new but thoroughly reworked for this company - is thrillingly compact and compelling. Panchenko is a marvel as her diamond-hard body scythes through Forsythe's high extensions, and Trevitt matches her, move for double-jointed move, while pretending cool indifference. For once it's not a fight or even a stand-off between the sexes. This is more enigmatic, and intriguing.

Christopher Wheeldon - another international catch - has expanded his earlier duet Mesmerics into a much longer piece using all five dancers. His style is gentler than Forsythe's yet full of memorable things - Panchenko hooping her body repeatedly around Nunn's waist, a slinky duet for Panchenko and Monica Zamora who move as a single body to goodness knows what silent click-track in their heads. The music is Philip Glass - full of tunes and texture, but given that it's all excerpts, I'm surprised Wheeldon made the work so long. You can have too much of a good thing, and less here would have meant more.

A duet for the two women by Cathy Marston was also striking, although the videoed commentary - about it being based on Lady Macbeth and Ophelia - was no help at all. But watching two such mesmerisingly beautiful women interlock in silky frocks hardly needs justification. Sometimes it's best to let bodies speak for themselves.

Nunn and Trevitt do this resoundingly in their signature duet Critical Mass - Russell Maliphant's endlessly absorbing, piston-driven paean to masculinity. And it's a tribute to their extraordinary partnership - symbiotic but wholly platonic - that their presence alone can bring the evening to such a satisfying close.

jenny.gilbert@independent.co.uk