This is an accounting dissertation, whose subject is the type of firm that dominated accounting developments in the UK and the US for most of the 20th century. Its focus is theory creation and most of the dissertation exposition does not focus on the theory per se. Instead, most of the exposition is devoted to communicating the pathway of the reflexive interpretation of the empirical materials relied on. Thus, the last chapter is the theory chapter, as it is the culmination and conclusion of theory creation. Theory creation relied on a qualitative research methodology (bricolage) that combined a specific concept of reflexivity, developed by Alvesson and Skèoldberg (2000) with a specific approach to engaging with empirical materials developed by Strauss and Corbin (1990). The empirical materials were drawn from three types of sources referencing the big accounting firms, academic research, the histories commissioned by the big firms and the intermittent disclosures of quantity 'stories' about the commercial operations of the firm. The theory created is an assembly of constructed concepts synthesising the various levels of reflexive interpretation of the empirical materials. It communicates a different vision of the firms; they are seen as a type of capitalist firm that has at least six enduring characteristics, all related to commercial action. These are capital management services production, client-focussed geographical orientation, partnership form, ethnic affiliation, prestige and knowledge base.