Spinetti's work in Joan Littlewood's Theatre Workshop produced many memorable performances including "Fings Ain't Wot They Used T'Be" (1959, by Frank Norman, with music by Lionel Bart), and "Oh, What a Lovely War!" (1963), which transferred to New York City and for which he won a Tony Award for his main role as an obnoxious Drill Sergeant. He appeared in the West End in "The Odd Couple" (as Felix); in "Chitty Chitty Bang Bang" in the West End; and as Albert Einstein in a critically lauded performance in 2005 in a new play, "Albert's Boy" at the Finborough Theatre. He launched his own one-man show of witty reminiscences, "A Very Private Diary", at the Edinburgh Festival Fringe.