In the early 1970s, Beaton began to perform in plays in London's West End. In 1970 he played the role of Ariel in Shakespeare's "The Tempest", which he described in his autobiography as "the most important role of my acting career", and also played a small role in the Frankie Howerd comedy film "Up the Chastity Belt" the following year. In 1975, he helped to establish the Black Theatre of Brixton. In 1975 Beaton played Nanki-Poo in "The Black Mikado", a modern version of Gilbert and Sullivan's "The Mikado".