David Keith McCallum, Jr. (born 19 September 1933) is a Scottish actor and musician. He is best known for his roles as Illya Kuryakin, a Russian-born secret agent, in the 1960s television series The Man from U.N.C.L.E., as interdimensional operative Steel in Sapphire & Steel, and for his current role as NCIS Medical Examiner, Dr. Donald "Ducky" Mallard in the series NCIS.