A “bureau-shaping model” is adapted to explain how the head of a control agency can shape its culture by agenda-setting, strategic recruitment and engaging staff in “expression games” through which their reputation depends on the impression they develop of competence and commitment to the core beliefs of the agency. The postwar shaping of a “culture of balanced evaluation” at the New Zealand Treasury (NZT) reflected the hegemony of a market failure paradigm. The NZT reinvented itself in the 1980s so that it would be aligned with a reformist advocacy coalition committed to impose and institutionalize a government failure paradigm. The accumulation of a number of threats to the NZT's authority appear to be prompting another reinvention as its current secretary seeks to bring it more into line with the appreciative leadership style of its centre-left government.