Sylvie Guillem and Akram Khan stand face to face, hands held, arms rippling in a winding ribbon of movement. Sacred Monsters is a meandering, sometimes self-indulgent show, but there’s real star power at its heart.

Both Guillem and Khan came to contemporary dance from classical roots: she as a superstar ballerina for the Paris Opéra Ballet and The Royal Ballet, he from the Indian classical form kathak. Khan also has a long history of collaborations with artists from other styles, from sculptor Antony Gormley to his recent show with flamenco dancer Israel Galván. Sacred Monsters, created in 2006, returns for one last time before Guillem retires from the stage next year.

Aged 49, Guillem is stepping down before she needs to. Her long limbs flow with unbroken line, her legs still swinging easily up to her famous “six o’clock” position. There’s no flashiness to the sky-high legs; her virtuosity is controlled and smooth, her timing exact. In one solo, she folds herself into syncopated angles while describing her fear that her work isn’t useful. The staging is informal, but Guillem’s stage presence is as strong as ever.

The spoken material is the weakest part of Sacred Monsters. You have to be a star to get away with this kind of chat; Khan and Guillem sound like Hollywood names exchanging cheesy scripted banter. They take a confessional tone before switching into aspirational slogans – Guillem, we learn, is glad that she still feels a childlike sense of wonder – or have little disagreements so they can overcome them.

The danced ideas are richer. As the lights go up on Shizuka Hanu’s set, a curling sweep of crumpled paper, we see Guillem wrestling with a long rope of bells, something between a musical instrument and manacles. Shadowing her, Khan jingles as he moves, with kathak ankle bells hidden under his trousers. Kei Ito’s costumes are simple tops and wide-legged trousers, modest and elegant.

Freeing himself, Khan moves into an intricate solo choreographed by Gauri Sharma Tripathi. His feet stamp through complex rhythms, his upper body moving like water. Guillem’s solo, choreographed by Lin Hwai-Min, is introspective but slight. She sketches a move, turns in on herself, sketches another. The music, played live on stage, is a mix of western and Indian classical styles, with fluent singing from Faheem Mazhar and Juliette Van Peteghem.

Sacred Monsters is at its best when the two stars just dance together, a meeting of styles and personalities. Guillem hooks her legs around Khan’s waist for a floating duet. She’s balanced rather than held, both leaning apart, reaching in different directions, echoing each other’s lines as they stretch into space.

Dance is full of romantic duets, but this is something else: it’s an image of a parallel journey. Their early training still shapes Khan’s and Guillem’s bodies, giving the same move a different accent. Winding around each other, they’re joined, but still distinct and individual. Two artists go exploring together.

Until 29 November. Box office 0844 412 4300