En Atendant is rarely thrilling. It is slow and lacks obvious shape, choosing not to please its audience with clear climax and development. There are few major shifts of energy or scene as it remains calm and considered throughout, requiring patience from its viewers. Some certainly found it challenging, with many walking out, but it is not the most difficult work of Anne Teresa De Keersmaeker’s career. It is densely packed, despite its tranquil exterior, with a fascinating array of patterns and combinations and some simple, beautiful dancing.

This piece was created to be performed at dusk at the medieval Palais des Papes in Avignon and followed at dawn by its twin, Cesena, performed at Sadler’s Wells later this week. De Keersmaeker has reworked both pieces for the proscenium arch and more friendly hours. The stage is simply divided front and back and side to side. Only the front is lit; the back is all darkness from and into which the dancers emerge and recede. A line of earth is piled in a flat line across the front, connecting the two sides of the space. The choreography and the design complement one another as the dancers move from side to side through the designated dancing space in the middle, and wait casually at the edges to go again.

Despite her reliance on music and its forms, De Keersmaeker is happy to present elements separately. It is a while before any dancing actually occurs. En Atendant begins with a flute solo, “L(ÉLEK)ZEM”, which features one sustained rising pitch overlaid with breathy notes. The sound remains unbroken for an impressively long time but occasionally waivers as the flautist Michael Schmid gulps in air. The solo stands separately from the whole, linked only by a simple framing device as Schmid’s deliberately laboured breathing to begin the evening is echoed by Mark Lorimer at the end. Following Schmid is the singular voice of Annelies Van Gramberen singing music of the medieval Ars Subtilior style; and then Chrysa Parkinson begins the dancing. Again the movement occurs in isolation. Despite taking its structure and inspiration from a fairly literal relation to the score the dancing is often performed unaccompanied, except by the squeaking of the trainers across the floor.

The aesthetic is one of clarity and conviction. The dancing is secure and uncomplicated by a need for extra motion, as is characteristic of much contemporary dance with faked, overindulged or overexpressed initiations and sensations. This is reflective of the composition, which shares this conviction and clarity. The movement switches between simplicity and complexity. Multi-dimensional actions are performed plainly and with purpose. The real depth lies in the counterpointing of the movement and the alignments and unisons that spark up between the dancers. Occasionally everything is stripped bare, pared down to a simple group-walking score, which is then embellished with more rhythmic and precise patterns of the feet.

Anne Teresa De Keersmaeker finds interest in a limited amount of material, performed repetitively with minor alterations in a complex score by the eight dancers. Occasionally the performers move into contact in a connected web of weight-sharing and counterbalancing grasps that link up across the group. The only break-out moment is when Bostjan Antoncic lets go and loses control, scattering the earthy barrier that had so far been almost entirely avoided.

There’s so much to see in En Atendant. You can cast your eye over the group and watch for connections, patterns and rules; or you can follow a single performer completing their simple yet exquisitely presented line of the score; or you can just get lost in it. I wish I could have seen the piece in Avignon, where I imagine it would have been totally different. Here on stage there was a flatness, one that I personally enjoyed, but outdoors in the historic setting and with the dwindling light En Atendant would have had a tangible, poignant charge.