Ken Russell's dizzy, affectionate homage to 1930s musicals and Busby Berkeley is for many his best film. Twiggy is the assistant stage manager who gets her big chance when star Glenda Jackson hurts her ankle. "Come back a star," the director tells her, and that's just what she does. (The same line was spoken by Warner Baxter to Ruby Keeler in 42ND STREET.) Russell's bombastic direction has never looked so right. Musical numbers (the film's song score received an Oscar nomination) are uniformly well done; included are renditions of old standards like "I Could Be Happy", "All I Do Is Dream Of You," and "You Are My Lucky Star." THE BOY FRIEND is a sincere celebration of the musical from a camp point of view. And let it be said Russell discovered Tommy Tune many years before Broadway did.