This is Not a Grail Romance provides answers to some of the most important questions surrounding the medieval Welsh Arthurian tale Historia Peredur vab Efrawc, one of the few surviving medieval Welsh narrative compositions, and an important member of the 'Grail' family of medieval European narratives. The study demonstrates that Historia Peredur is an original Welsh composition, rather than (as previous theories have suggested) being an adaptation of the twelfth-century French grail romance. The new analysis of the structure of Historia Peredur presented here shows it to be as complex as it has always been thought - but also more formal, and the result of intentional and intricate design. The seeming inconsistencies or oddities in Historia Peredur can be understood by reading it in its medieval Welsh cultural context, allowing the modern reader a greater appreciation of both the narrative and the culture that produced it.