jats:titleABSTRACT</jats:title>jats:pA renewed interest in aspects of high politics among historians who subscribe to the ‘new political history’ has coincided with the embrace by some political scientists of interpretivism as a method for understanding how beliefs and traditions impact on British political life. In order to examine the potential synergies between these two developments, this article utilizes a form of ‘historical interpretivism’ to study the beliefs and actions of senior civil servants. In 1980, the British government released a Memorandum of Guidance for Officials Appearing before Select Committees – known ever since as the ‘Osmotherly’ rules – to help civil servants navigate the stresses of appearing before parliamentary committees. This article analyses the civil service files in the decade leading up to the publication of the Osmotherly rules to reveal how senior civil servants sought to reconcile their interpretations of Westminster tradition with the need to respond to the demands of the ‘open government’ agenda. The article argues that studying the narratives which guide the beliefs of individual civil servants and their political masters can help political historians and political scientists alike analyse the power of tradition in shaping political action.</jats:p>