The office of Speaker has generally been seen as having an almost accidental origin (in the British House of Commons) and non-deliberate design and development. Save for the simple dichotomy made between the US-style Speaker and the British Speakership, little detailed analysis of this office has been undertaken. This work looks at the office form the perspective of rational choice new institutionalism. Our empirical focus is on the Irish Speaker (Ceann Comhairle). Having justified the new institutionalist approach, we develop a rational choice account of the office From this account we then postulate a series of empirically testable hypotheses. Using data collected from parliamentary records and other sources, it is shown that, far from being a neutral arbiter, the presiding officer is an asset of the governing parties. The research explores many issues at the core of legislative politics including the motivation of political actors, the origin and development of institutional arrangements and the consequences of particular institutional types. As such, the research provides novel and empirically tested arguments that challenge much of the conventional wisdom regarding both political actors in the legislative arena and the paradigms used to understand them