MacMillan’s first ballet Somnambulism revealed a precocious young talent. The anxieties it explored were rooted in MacMillan’s own; he would return to these anxieties and elaborate them in many of his subsequent works. Made in a week to fill a gap at a choreographic workshop, Somnambulism was the success of the evening. It was set to three jazz pieces by Stan Kenton, rearranged by the conductor John Lanchbery.
Somnambulism’s three main characters, were portrayed as if in dreaming sleep, variously troubled by anxiety, monotony and premonition. A corps de ballet of six wore black masks to transform them into the faceless fantasies of the three dreamers.
MacMillan created the leading female role for Maryon Lane, and he himself performed as one of the two men. This was a late change: because Margaret Hill, the intended dancer, was ill on the day, MacMillan adapted her steps for himself, making impromptu improvisations. Lane, who danced Premonition, was menaced by gloved hands reaching out from the wings. When she grabbed at a hand, a body fell dead at her feet. She believed herself responsible for the man’s death, watching in horror as his corpse was carried across the stage in a mock funeral procession. In the solo representing Monotony, David Poole danced the same step over and over, “a study of a young man rocked by conflicting emotions, as if in a brainstorm, being mentally tortured” (Dance and Dancers).
Lane recalled that the ballet was prepared in a small room at Sadler's Wells Theatre so cluttered with skips and wardrobe baskets that the floor space was barely eight feet square. For the workshop presentations, De Valois had stipulated that sets and costumes were to be kept simple. Somnambulism’s cast wore practice dress, their only props black masks and white gloves.
For the dance writer Peter Brinson, Somnambulism was “clear-cut, precise, highly original in construction and very demanding on the dancers”. Clive Barnes thought it “obviously the work of a new choreographer potentially of the first rank”’. As The Dreamers, it was subsequently performed live on BBC TV, with the score played by the Ted Heath Orchestra. In 1956 it was briefly taken into the repertory of the Sadler’s Wells Theatre Ballet.
In March 1953, the magazine Dance and Dancers featured MacMillan as its Personality of the Month and applauded his talent. “His remarkable invention of movement, understanding of mood, sense of theatre and how to use a stage, make this one of the most mature first works we have seen”. With this success behind him, MacMillan joined his friend John Cranko as a choreographer for Sadler's Wells Theatre Ballet and for Covent Garden. Within a short time, British ballet, still in its nascent state, had produced two choreographers who would prove to be major artists.