Interrogating the physical fabric of the structures that comprise Hadrian’s Wall continues to be a focus of scholarly endeavour. The four papers forming the core of this volume tackle three very specific elements of these structures. Two were written by Derek Welsby, with the first examining how the ground plans of two of the installation types found along the Wall — the adapted fortlets known as milecastles, and the towers known as turrets — were laid out. His second contribution is dedicated to determining whether the milecastles had towers above their gateways. The remaining papers were penned by the late Paul Bidwell and Nick Hodgson respectively, to examine aspects of the evidence for a wall-walk along the curtain.

Of the subjects addressed here, the one that has generated the greatest degree of scholarly interest is the question of whether the Wall curtain carried a wall-walk. This enduring fascination is reflected by Bidwell’s contribution, which was first published in 2008 and is reprinted here. Anyone keenly interested in the subject will be familiar with it, as engaging with the arguments he presents remains essential for any serious treatment of the subject. Bidwell ranges widely, bringing together topics such as the widths of the curtain, the integration of bridges, architectural elements from otherwise lost elements of superstructure, projectiles found in Wall posts, and comparanda from elsewhere in the Roman and Hellenistic worlds. Hodgson’s contribution augments this by delving deeper into the chamfered stones from a string course, while simultaneously contributing to the ongoing scholarly debate about a wall-walk, which has continued since Bidwell’s paper was originally published.

Both Bidwell and Hodgson use the available evidence to assemble persuasive cases for the existence of a wall-walk. Your reviewer agrees that one was probably present, although a number of respected specialists feel the evidence points in the other direction. In the case of the chamfered string course, a key point is that when comparable stones are found in forts, they are associated with the transition from the curtain wall to the parapet. The recovery of such stones in large numbers from the Wall curtain therefore supports the presence of a wall-walk, and Hodgson goes on to suggest that the parapet was ‘almost certainly crenellated’, in part because there ‘is no ancient parallel’ for an uncrenellated parapet (86). Fallen masonry may well provide clarity on this matter one day, but for now there is some scope to wonder if a flat-topped parapet was provided, as the late Peter Hill and Brian Dobson discussed. Bidwell and Hodgson acknowledge that merlon cap stones have come from forts and turrets, rather than the curtain — in contrast to the chamfered stones. A set of decorative pans, including the Rudge Cup, present the strongest candidates for contemporary representations of the Wall. If so, they are heavily stylised and depart from reality in places — not least by omitting the regular gateways that pierced the curtain — but it may be significant that all of the known examples distinguish between what appear to be crenellated turrets and a flat-topped curtain. As Bidwell and Hodgson observe, none of this need equate to an absence of crenellations. Even so, other facets of Hadrian’s Wall demonstrate that new approaches were attempted, so we could perhaps wonder if there was something about local conditions in this frontier zone that made a flat-topped parapet acceptable.

Welsby’s examination of milecastle gateways also proposes a potential departure from what might be considered standard practice. Study of fortlets suggests that a tower was usually — though not universally — present at gateways, presumably as part of its normal defensive architecture. Where a tower was seemingly absent, as in the east gateway at milefortlet 21 on the Cumbrian coast, the traces of the entrance structure can be slight indeed. This is not the case with the milecastles, which typically contain paired north and south gateways that are approximate mirror images in plan. Welsby martials an impressive range of data to assess what sort of superstructure could have risen above the height of the surviving masonry. Numerous important observations flow from this, making his paper a valuable addition to the literature on milecastles in general and their towers in particular. While Welsby ultimately favours the possibility that the milecastle gateways did not have towers, he observes that structurally ‘the most relevant parallels are the chambers assumed to be set over the portals of fort gateways’ (140). A comparable provision at a milecastle would create an enclosed chamber at wall-walk height, while an accessible flat roof and parapet above it would allow a soldier to stand at third-storey level. As Hill and Dobson observed, some milecastle gateway passages extend farther than is necessary to accommodate the individual gate leaves, which seems most easily explained as a means to increase the floor area of an upper element.

When it comes to assessing how the ground plans of milecastles and turrets were laid out, Welsby and Hodgson suggest in their brief introduction to the volume that this paper ‘is probably the least contentious as it is based entirely on observed and recorded evidence revealed through excavation since the 19th century’ (1). Some limitations with these data are discussed, and it is certainly true that not all measurements of Hadrian’s Wall produced over this period are as consistent as we would wish. A quick survey, for example, reveals four varying sets of published dimensions for turret 44b, which differ in turn from measurements taken from the detailed plan of the visible remains made in 1989. Although the discrepancies are sometimes subtle, it emphasises that a selection process can be necessary. Welsby states he usually takes his dimensions from the excavators’ original published plans, which he describes as ‘not ideal’ (6). These plans are a mixed bag; some are excellent, some were published small, and one is characterised by Welsby as ‘appalling’ (25). Use is also made of a few of the detailed plans of visible structures produced in the 1980s and 1990s. It is a shame that only some of these are easily accessible to researchers. Welsby’s considered and thought-provoking analysis of his dataset examines how these structures can be grouped, and whether they were laid out using pes monetalis or pes drusianus.

Much of the analysis of the Wall structures in this volume serves not only to offer a fuller understanding of them, but also to shed light on the potential purpose of the frontier system. The possible wider implications of interpretations proposed here are discussed by all of the authors, ensuring that this volume makes an important and stimulating contribution to the ongoing scholarly debate about what the Wall was intended to achieve. The results showcase the enduring potential for detailed studies of the physical fabric of the Wall to inspire fresh thinking.