Sacred Monsters, Khan/Guillem, Sadler's Wells

There is a special poignancy to these performances of Sacred Monsters, Sylvie Guillem and Akram Khan's terrific 2006 joint show.

Guillem, the former Paris Opéra étoile and Royal Ballet prima ballerina whose singular talent has lit up contemporary dance for the last decade, announced in October that she will be retiring from the stage for good in 2015.  Sitting in Sadler's Wells last night I was achingly conscious not only that this was probably the last time I would see Sacred Monsters, but also one of the now vanishingly small number of opportunities left ever to watch Guillem, one of the truly extraordinary dancers of our (perhaps all) time.

Apart from her distinctive leggy, extremely flexible body, one of Guillem's distinguishing characteristics as a performer is her directness – the strong will that frustrated successive Royal Ballet directors, but also the honesty that sees her smile with touchingly genuine relief and delight at audiences while she takes her curtain calls. Khan is even more confessional on stage, frequently revealing his thoughts out loud by talking between dance numbers, and one of his most successful and well-loved works was the autobiographical DESH (2011). As much as their incredible physical talents, it's the generosity and seriousness which both Khan and Guillem bring to performing that has made them into stars; audiences trust them and like them, as well as admiring them.

There's enough of dance's joyful power on display to make you believe it's worth all the anxietySacred Monsters captures all the reasons for this as well as anything else I've seen either of them do. The term itself was coined for the Parisian stage stars of the 19th century, and captures the expectations heaped on major celebrities, as well as their potential depersonalisation; they can become freak-shows or mere executors of rituals, their individuality and freedom of expression swallowed up by the parts their worshipping fans expect them to play. Khan and Guillem know this pressure well, and in calling their show Sacred Monsters allude perhaps to the ease with which they could have given in to it, by parading a stock collection of typically "Sylvie" (classical ballet) or typically "Akram" (Kathak) routines, like Anna Pavlova doing the Dying Swan over and over again for decades.  

But instead Sacred Monsters insistently foregrounds their individuality, even (somewhat disingenuously) their ordinariness: Khan tells us about going bald, and his mother's pet name for him, while Guillem reveals her worries about futility, and her desire to retain a sense of childlike wonder. The two of them have an engaging, odd-couple rapport, which is often delightfully comic in dialogue, and even in dance. Surely, no-one's heart can fail to be warmed by a sequence in which Khan and Guillem, bobbing gently to a simple beat, do a kind of robot boogie, for all the world like a pair of teenage mates exuberantly throwing shapes on the local club dancefloor on a Friday night.

It's not all giggles and confessional comedy, of course: the pressures exerted by the stage and classical dance traditions on their sacred monsters are very real, and the anxiety caused is serious. Khan and Guillem show it to us in nervous tics that flicker across their bodies as they talk, or in tense solos – Khan restlessly pressing his head and shoulders into the ground, Guillem showing us glimpses of beautiful ballet attitudes and arabesques, then falling out of them into whirls and lunges, like a judo player always on the defensive. They even fight each other at points, Guillem goading a tired Khan when he refuses to dance, Khan retaliating by headbutting her to the ground. 

But both comedy and combat are in the end subsumed into a greater peace, a kind of sacramental serenity supplied by the dance itself. Khan has said in interviews that as soon as he's dancing he's in the present, released from fear of the future, and it's this timeless feeling I took away most strongly from Sacred Monsters. From a wonderful Kathak solo by Khan, in which string upon string of glorious rhythms spin out from his feet (poetry jamming for the body) to the hypnotic duet in which Khan and Guillem's linked arms ripple like water, there's enough of dance's joyful power on display to make you believe it's worth all the anxiety, at least for these two.

Khan and Guillem are not the only performers on stage, and enormous credit must go to the five musicians who create the soundworld for the dance. They're an international bunch (Belgian vocalist Juliette Van Peteghem, German percussionist Coordt Linke, Pakistani vocalist Faheem Mazhar, Australian violinist Alies Sluiter, and British cellist Laura Anstee) and the music too seems to float across national boundaries: Indian singing on top of Western string instruments ends up sounding almost Celtic, especially in the warm, storytelling tones of Van Peterghem and Mazhar's voices. 

Shikzuka Hariu's set is two enchanting curves of crumpled paper, pure white, which recall rock walls; in this setting and under the frequently very bright lighting of Mikki Kunttu, Khan and Guillem came to seem to me like inhabitants of a sacred mountain, and dancing a vector of the divine encounters that happen in high rocky places, sometimes challenging (like Jacob wrestling the angel), sometimes benedictory (Mohammed receiving revelation from Gabriel), and sometimes both personal and peaceful, as hermits and holy men of all religions have found.

Few are the dance shows of which one can genuinely say "I didn't want it to end", but Sacred Monsters stopped far too soon for me; pure delight cut off in mid flow. Go and see it if you can; this one is truly unmissable.

• Sacred Monsters is at Sadler's Wells until 29 November.