His varied screen roles included Thomas More in the 1969 film version of Maxwell Anderson's play "Anne of the Thousand Days", Sir Daniel Brackley in the 1972 television adaptation of Robert Louis Stevenson's "The Black Arrow", the voice of Gandalf in the 1978 animated version of "The Lord of the Rings" and the Shadow in the 1979 "Doctor Who" serial "The Armageddon Factor". Perhaps his best-known role was as Hunter, the superior of secret agent David Callan in the spy series "Callan" in the early 1970s; Squire took over the role from Derek Bond.