In this paper we offer an empirically rich, longitudinal account of the role and influence of externally sourced experts by the Swedish development aid agency, Sida, from the 1960s until present times. We describe what type of expertise has been required from external experts and how the content and rituals of these contracted experts have contributed – or not – to perceptions of trust and certainty. In the paper we present three eras, all with their distinctive features on the normative rationale and forms for external expertise; 1. 1960s–ca 1995: the Quick-fix implementer era; 2. Ca 1995–ca 2005: the Collaborative turn era; and 3. Ca 2005–2020s: the Proper organization proxy era. We suggest that a mission drift has occurred in Swedish aid as concerns both the in-house expert role of aid bureaucrats and the role of procured experts. The paper concludes that all throughout, external experts have served an important function – that of making organizations in the donor role less uncertain of their decisions on which organizations should receive funding. Interestingly, however, the use of external experts has in all times given rise to additional uncertainty, which, in turn, has called for even more experts. We also find that external experts have repeatedly been criticized for ineffectiveness and consultocracy, meaning that consultants have been influential in the formulation and implementation of policies aimed at restructuring public services.