Though Williamson's screen output has been relatively spare, he has turned in several outstanding performances, playing an angry young businessman in "The Reckoning" (1969), a cocaine-sniffing Sherlock Holmes in "The Seven-Percent Solution" (1976) and a scatterbrained Merlin in John Boorman's "Excalibur" (1981). He made his American TV debut as Lenny (opposite George Segal) in an adaptation of John Steinbeck's "Of Mice and Men" (ABC, 1968) and has portrayed a number of historical figures for the small screen, including Richard Nixon ("I Know What I Meant", Granada TV, 1974), King Ferdinand ("Christopher Columbus", CBS, 1985) and Louis Mountbatten ("Lord Mountbatten: The Last Viceroy", PBS' "Masterpiece Theatre", 1986). Williamson played the ghost of John Barrymore on Broadway in the short-lived "I Hate Hamlet" in 1991 and returned to the Great White Way in 1996 as the legendary actor in a one-man show of his own creation, "Jack--A Night on the Town with John Barrymore", prompting some wags to pose the question, "Who is Nicol Williamson going to slap now that he's acting by himself?"