In this ambitious book Ardis Butterfield reassesses and ultimately challenges a number of prevailing beliefs concerning the coexistence, development, and rivalry of English and French in England, focusing especially on the period of the Hundred Years War, but actually covering a much broader chronology spanning the twelfth to the fifteenth centuries. She maintains — and offers a massive amount of convincing evidence to support her argument — that the literary, political, and cultural force of French in medieval England and the cross-channel connections that it generated are far more complex and influential than commonly believed. 'The heart of my study concerns what it means to be English and French in the light of this common possession. Sharing a language and a literature crucially confuses a clear sense of distinction between English and French' (p. xxi). Although all ten chapters make significant contributions, I consider the ninth, 'Mother Tongues: English and French in Fifteenth-Century England', to be the most compelling and important. Butterfield develops here one of the major theses of her study: French should be considered an essential part of the English vernacular throughout the medieval period. 'It is the continuing argument of this book that if we broaden our attention to English vernacularity and see it as including French then English precisely changes its shape' (p. 317). She examines various pedagogical treatises intended to help English readers improve their mastery of French, in particular the Manières de langage (1396), which remained popular well into the fifteenth century. It has been suggested that the existence of these teaching manuals reflects an attempt to counteract the decline of spoken French in England during the late medieval period. Butterfield skilfully deconstructs this argument, demonstrating the weaknesses of its logic and suggesting that the opposite conclusion is equally plausible. The Manières de langage, she reminds us, teaches not only grammar, but also includes numerous samples of spoken French: for example, how to address a merchant, or labourers, how to answer a beggar, how to ask for a room in a hostel. The manual, she concludes, is intended for the use of those who already speak French with a reasonable degree of competence and who wish to strengthen and refine their oral proficiency. Pedagogical treatises of this nature, she argues, 'are not so much a sign of an imperfect and fading grasp of French trying vainly to resurrect itself as a lively knowledge, but rather a radical desire to re-ground an existing lively oral knowledge of French' (p. 335). Butterfield contends that historical considerations of English tend to neglect the importance of French as the other vernacular in the [End Page 476] medieval period. By the same token, studies of Chaucer tend to neglect the French heritage that partially shapes his work. Without exaggeration, it can be said that Butterfield advances several groundbreaking arguments, which she articulates with admirable clarity and supports with impressively meticulous documentation. The prevalence and influence of French as a written and oral vernacular in medieval England will need to be reassessed in the light of her research.