 Guillam is half-French and half-English, and comes from a family that has worked for The Circus (le Carre's name for MI6) for generations.Although "Call for the Dead" indicates that he served in World War II, the later books in the series indicate that he was born around 1933.Although he has done observational "field work" in the past and recruited spies that report to him, Guillam himself is uncomfortable with getting personally involved in spying operations, preferring an administrative role.