Existing scholarly accounts of the origins of the archdiocese of Hamburg-Bremen, which would ultimately claim ecclesiastical authority over the whole northern world, are heavily dependent on Rimbert's Life of Ansgar, written some time after 865. According to Rimbert, it was Charlemagne who originally conceived of a northern archdiocese to convert the Swedes and Danes, and his son who brought this plan into fruition in 831 when he made Ansgar the first archbishop of Hamburg. Following a devastating attack on Hamburg in 845, and the timely death of Leuderich of Bremen in the same year, Bremen was united with Hamburg so as to provide the impoverished mission with material support. Although some scholars have questioned aspects of Rimbert's account, none have yet done so as comprehensively as Eric Knibb does in Ansgar, Rimbert and the forged foundations of Hamburg-Bremen. Deferring an analysis of the Life of Ansgar until the final chapters, Knibbs sets out the ecclesiastical and political background of the northern mission and then proceeds to reconstruct an alternative history of Hamburg-Bremen based on the less-studied foundation documents of the archdiocese. Knibbs combines a meticulous analysis of these sources with a good sense of the wider events which shaped the formation of the archdiocese, from Ebo's role in founding the mission and his ultimate fall from grace, to the division of the empire in 843 and the tangled politics of Lothar ii's divorce case. The narrative that he proposes is far messier than that suggested by Rimbert, and rather more plausible. Knibbs presents the archdiocese of Hamburg-Bremen as being insinuated into existence by the forgeries of Ansgar and his successors, determined to survive long after support for the mission had withered away. Changing circumstances necessitated new visions of what the archdiocese actually stood for, and successive archbishops ‘updated’ older documents, creating revisionist histories to defend their institution. In time these fabrications came to be accepted and confirmed by popes and kings, and continue to have an undue influence on historians. In setting out the case for a far more nuanced understanding of the origins of Hamburg-Bremen Knibbs achieves what he sets out to do, and the only points of criticism here are those which could be applied to almost any historical work: the originality of the argument is at times slightly overstated; and there is some relevant scholarship of which Knibbs appears unaware, particularly when he deals with issues more distant from his core argument. Knibbs uses the footnotes and a short appendix to discuss points of detail and supplies a useful bibliography of relevant material in English, German and Latin. Crucially, Knibbs' argument works, making Ansgar, Rimbert and the forged foundations of Hamburg-Bremen essential reading for anyone interested in the history of Hamburg-Bremen or any of the remarkable texts produced there. Its accessible style and structure, along with Knibbs's good sense of context, opens up the work to a wider audience, and anyone concerned with medieval missions or forgery, or with the Carolingian kingdoms in the ninth-century, will find much of great value here.