There is something for everybody in Keith Ray and Ian Bapty's Offa's Dyke. Archaeologists will appreciate the site descriptions and the updates on the last decades of survey and excavation. The extensive discussion of coins, charters and narratives, written long after king Offa of Mercia died in AD 796, and the insertion of the Dyke in a Frankish, Carolingian context, will cheer early medieval historians. Avid hikers too will find much of interest between the book's covers, beginning with the careful maps and the topographical index, although at 448 heavy-paper pages, it is a bigger and heavier volume than most will want to carry in their rucksacks. Aesthetes will admire the hundreds of fine photographs and drawings of landscapes and artefacts, meticulously labelled and cunningly worked into the text—a model of modern publishing craft. And of course Offa's Dyke enthusiasts will be delighted to find so much previous scholarship on the object of their enthusiasm gathered together, summed up and assessed fairly. The authors refer often to Sir Cyril Fox (died 1967) and his pioneering labours to understand and publicise the Dyke. A remarkable 1924 portrait of the great archaeologist, grinning and cradling a human cranium, is reproduced at the book's outset, alongside the authors’ dedication of the book to his memory. Yet ironically, Ray and Bapty may have rendered Fox's classic Offa's Dyke (Reference Fox1955) superfluous, so compendious is their account of the monument and the investigations of it.

Offa's Dyke is well organised. It has three sections, one on the available evidence and previous study of it (Chapters 1–3), one on how the Dyke was built and managed (Chapters 4–6), and one on the historical context, within which Ray and Bapty would like to see the Dyke reappraised (Chapters 7–9). All three sections are somewhat plodding as a result of the aspiration to be all-inclusive, although the thick description of the current state of the Dyke in the first section is the densest (Chapter 1). But as with the subsequent description of what people have thought about the Dyke over the past millennium (Chapter 2), that account—in effect a linear field survey—is valuable. It is the basis for Ray and Bapty's claim that the Dyke is longer and more complete than most modern researchers allow, and that features previously thought to be signs of haste or incompetence actually serve to improve visibility from the Dyke and provide a more imposing ‘stance’ for anyone who contemplated it from the west (the Welsh). That is the thrust of Chapters 4–6, wherein the authors present what they consider to be their “most potentially significant” (p. 165) contribution to Offa's Dyke Studies, namely the observation that the Dyke was very sensitively placed in the landscape (they call it “adjusted-segmented construction”, p. 203). In the last three chapters of Offa's Dyke, Ray and Bapty develop their maximalist position on the nature and purpose of the Dyke, suggesting that it was both a symptom and an instrument of Mercia's “hegemony” (p. 333; they admit that word is not just murky but “mercurial”, p. 103). The most original aspect in their optimistic assessment of eighth- and ninth-century state activity in Mercia is their insistence on the importance of Offa's successor, Coenwulf, for the history of the Dyke.

Ray and Bapty's Offa's Dyke reflects the ongoing scholarly rehabilitation of the post-classical period. Debates between those who consider the centuries after Rome's fall positively (‘continuitists’) and those who deem the Dark Ages a major retrogression (‘catastrophists’) are muted now; a more stable and wealthy early Middle Ages tends to prevail. The capable Mercian regime that, in Ray and Bapty's opinion, confidently designed and built a massive earthwork—at Ruabon, the bank can be 10m higher than the ditch floor—from Flintshire to Gloucestershire is a product of this historiographical trend. Whether the Mercian courts of Offa and Coenwulf had a subtle frontier strategy in mind, and command of the resources to execute the strategy, is of course uncertain. But Ray and Bapty gallantly make the case for seeing Mercia as a rival of Charlemagne's empire, and in these times of British Euroscepticism, their ‘European Offa’ is attractive.

In their discussion of the Dyke, Ray and Bapty try to avoid the pitfall of circular reasoning. But when one takes an artefact (Offa's Dyke) as evidence of something (hegemony) and then uses that something to interpret the artefact, it is difficult to avoid circularity completely. To their credit, even when offering maximalist interpretations of the Dyke structure (which is rather difficult to discern along much of its purported course) and its function, the authors point out the possible counter-arguments and consistently use ‘maybe’, ‘possibly’, ‘may have’, ‘probably’ and similar cautious phrases. They also signal that their recourse to Wat's Dyke (a shorter earthwork that follows the northernmost section of Offa's Dyke) in order to make Offa's effort a more complete Welsh border is debatable, and that not everyone will see in Offa and Coenwulf's coinage, or in the Staffordshire hoard, relevant evidence for reading the Dyke as such. They also duly note that there is no sign that the Dyke was maintained or used after its completion, and they acknowledge that there is still no archaeological reason to place the construction of all of the components of the Dyke in the eighth century.

Ray and Bapty claim that their goal is to “provide a reasonably comprehensive ‘baseline’ statement of current knowledge and understanding” (p. 4) of Offa's Dyke. This pursuit of encyclopaedic coverage can obscure the authors’ own argument: as few previous interpretations of Offa's Dyke get ruled out entirely, one sometimes wonders where they stand. Unlike the earthen monument itself, interpretations of it have proved ephemeral, dependent on chance finds, unsystematic excavation, the analysis of scanty coeval written records and the ideology prevailing at the time of interpretation. Ray and Bapty's Offa's Dyke usefully synthesises available data and proposes a concept of the builders’ “real purpose” (p. 297). But it is unlikely to be the last word on an enigmatic and poorly documented structure. Indeed, the authors humbly say that they wrote the book in the hope of stimulating new interest in a landscape feature dear to their hearts.