This work is for comparative linguists and celticists who are keen to study Breton but may be too daunted to undertake such a venture by the wide variety of orthographical conventions which exist in Breton. The chronological development of the Breton orthographical debates during the twentieth century is charted along with an attempt to discern the ideological, political and personal motivations which lay behind those debates. Based on a substantial corpus of hitherto unpublished original documents and personal interviews, the research throws new light on the nature of the political, ideological and linguistic divisions of the Breton movement of that period (not least the events that occurred during the 1939-45 war). The historical and societal background of the language is succinctly delineated and points of orthographical contention are discussed, each in turn, so that their correlation to the spoken varieties of Breton can be judged by the reader. The work should dispel once and for all the notion – boosted by the existing orthographical instability and variety – that Breton is too dialectally fragmented to be studied profitably without an inordinate amount of effort.