This book starts with a simple question: is it possible to identify the direction in which Dere Street was planned? To answer this, Poulter builds on an equally simple premise: the rounded topography of northern England and southern Scotland means that the highest elevations do not always provide the best views for planning. P. therefore contends that if Roman surveyors were following an existing alignment, they would continue over the summit of a hill before changing direction at a brow which afforded a convenient forward view. By personally observing the visibility of the landscape from the points where the road changed alignment, it is possible to surmise the direction in which the planners worked.
In the grand scheme of things, the sceptic might well ask why it matters whether Dere Street was planned from south to north or vice versa. The ensuing analysis, and its extension to the frontier works, quickly demonstrates how deceptively simple that question is and the valuable conclusions which can be reached by detailed consideration of these alignments. Through a combination of map work and field observations, P. argues that these monuments demonstrate multiple phases of planning and were laid out with a variety of methods which indicate distinct objectives.
Much of Dere Street was planned in two main stages: first a series of long-distance alignments was established; then a series of deviations was added to avoid obstacles or to find appropriate river crossings. The long-distance planning proceeded from south to north with the secondary deviations then planned in either direction. The subsequent construction work introduced an additional series of deviations based on local line-of-sight adjustments. Some of these latter modifications compensated for inaccuracies requiring short correcting curves.
Applying the same technique to Hadrian's Wall and the Vallum reveals contrasting planning methods and differing priorities. The route of the Wall seems to have been determined by the Whin Sill crags and the river crossings over the North Tyne and Irthing. The planners worked from the extremities of the Wall inland towards these fixed points, again using long-distance alignments with secondary deviations. (P. notes that his method cannot resolve the debate over the location of the original eastern terminus or indicate the direction in which the Wall was actually constructed.) Importantly, P. observes that the planned route of the Wall almost always maintains a dominant view to the south rather than seeking out a line with better visibility to the north. Overall, he argues that the course of the Wall is a compromise between several objectives, but that this southerly aspect suggests that the primary determinant was signalling and communication to the forts behind the Wall. P. stresses this by providing an alternative route which would have been more apposite if the aim had been to optimize visibility to the north. In contrast to the unity of the Wall's long-distance planning, P. argues that the Vallum was planned piecemeal from the nearest Wall fort making greater use of line-of-sight alignments and with little regard for its landscape setting.
The Antonine Wall presents yet another planning method, indicative of different objectives again. For a number of reasons, the evidence is more problematic than for the previous monuments; for example, there are many more changes of direction but fewer have been excavated. Nonetheless, P. argues there was no long-distance planning. Instead, the route comprised many short alignments which could have been achieved by line-of-sight planning. He is therefore inclined to believe that, unlike Hadrian's Wall, the Antonine Wall was planned to link up a series of existing forts (even if these were only planned and not yet constructed).
P. discusses the caveats rigorously; for example, he notes the problems inherent in the mapping upon which he relies, including potential confusion caused by General Wade's reuse of Hadrian's Wall for his Military Road and the way in which earlier mapping of the Antonine Wall depicted a more sinuous route rather than a series of short, straight alignments. He is also careful not to push his conclusions further than his observations permit; for example, the forestry and modern development which obscure parts of the Antonine Wall make him more cautious in his conclusions by comparison with those for Hadrian's Wall.
The volume concludes with a short report by McKeague on the history of cartographical representation of the Antonine Wall which serves to illustrate some of the issues raised by P.'s research. Comparison of different Ordnance Survey maps demonstrates how the objectives of cartographers and the selection of map scales and symbols influences perception of ancient monuments.
P. has provided us with a welcome and original perspective on the military landscapes of northern Britain. From a simple question and basic methodology has developed a nuanced insight into the constantly evolving objectives of the Roman army and the inventive ways in which the military planners responded to these requirements on the ground.
