The pieces — ranging from “Baiser de la Fée” (1960) to “The Judas Tree,” created a few months before his death — were performed by Britain’s five major ballet companies: the Royal Ballet, English National Ballet, Scottish Ballet, Birmingham Royal Ballet and Northern Ballet. (The small Yorke Dance Project also came to the party, with an intriguing revival of an almost unknown 1988 chamber piece, “Sea of Troubles,” inspired by Shakespeare’s “Hamlet.”) This collaboration, the idea of Kevin O’Hare, the director of the Royal Ballet, was in itself unusual. Several of these companies seldom come to London, and they almost never share a stage or an audience.

MacMillan, in his desire to rend the decorous veil of ballet, is often seen as the polar opposite of the other major 20th-century British choreographer, Frederick Ashton, whose refined, lyrical and witty pieces (“La Fille Mal Gardée,” “Symphonic Variations,” “Sylvia”) came to define the pre-MacMillan era of British classical dance.

“Kenneth MacMillan was the dark genius of British ballet — its destroyer, if you listen to some,” the critic Ismene Brown wrote in an article about the celebration in The Spectator magazine.

But it wasn’t just MacMillan’s subject matter, which could include rape (“The Invitation”), incest (“My Brother, My Sisters”) and sexual sadism (“Mayerling”), that bothered critics. It was also his use of ballet technique to suggest states of extreme emotion and erotic desire. In 1981, in a piece about the Royal Ballet’s 50th-birthday season at the Metropolitan Opera House in New York, Arlene Croce wrote that the danger to the “pearly classicism” of the Ashtonian style “is from this new religiose preoccupation with the human body and its contortions which is now so pronounced in MacMillan’s ballets.”