The evidence for the construction of canals in England in the tenth and eleventh centuries has been gradually accumulating since the 1980s. It was drawn together by John Blair (Reference Blair2007) in an edited book that argued for the widespread construction of early medieval waterways. While there were a few documentary references to canals, the papers in that volume demonstrated that further examples could be identified from archaeological fieldwork. For eastern England, much of the evidence for early medieval canals had already been identified by the Fenland Survey. Somewhat surprisingly, the discovery of these was not much discussed in the final synthetic volume on the Fens, although the implications were significant (Hall and Coles Reference Hall and Coles1994). There was a certain reluctance among archaeologists to accept that large-scale construction works, involving precise levelling, could have been undertaken as early as the tenth century.

The existence of Anglo-Saxon canals has now been largely accepted, and more recent research has focused on when such watercourses, whether for transport or drainage, were built and how extensive they were. Chisholm approaches this question as a geographer, distinguishing between natural distributaries of the rivers and artificial watercourses. He argues that a series of watercourses were built before ad 1000 to drain the River Nene through the marshlands and provide routes along which goods could be transported. He suggests that this was a unified project that required the construction of more than 60km of watercourse. The most likely context for this work was the foundation or re-foundation of abbeys at Crowland, Ely, Peterborough, Ramsey and Thorney around 970. If the artificial origins of these channels are accepted, then it seems likely that a further 75km of watercourses were built for purposes of drainage or to allow the abbeys to move goods. Indeed, the total length identified by Chisholm is even greater.

The consequences of these vast works are examined in the final chapter. It is suggested that the programme of construction was an extraordinary co-operative project initiated by King Edgar to transform the Fens. The idea of the abbeys as remote religious houses established to foster strict worship in conditions of extreme austerity is hardly compatible with Chisholm’s analysis. Instead, the abbeys have to be regarded not as accidental agents of change, but as the instruments of political planning to colonise an underdeveloped area of the kingdom. This dirigiste view is hard to swallow at first reading, although it is only a small step beyond the widely accepted realisation of the efficiency and organisational capacity of the late Anglo-Saxon state. Instead of looking upon the kingdom just as an effective collector of taxes, in the light of this work we must regard it also an active agent in the production of agricultural wealth.

The practical problems of undertaking such vast works are touched upon only briefly. First, there were the difficulties of surveying the lines for the watercourses. That work required lines, some of them straight, to be laid out across fenland with carefully chosen routes. Then there was the problem of finding sufficient labour to cut the channels in a sparsely occupied area of the country. It is only possible to speculate how such a body of people, perhaps to be numbered in their thousands, were accommodated and fed.

The argument of this volume is constructed in a dry, painstaking manner, and can be particularly critical of other scholars. ‘An inherently implausible proposition’ and ‘the claim is a non sequitur’ are two phrases used about others’ work. Yet the conclusions drawn here also rely on inference and interpretation, although they are asserted in a forthright manner that implies there can be no doubt. Documentary sources are treated as if they provide incontrovertible proof, although every historian knows that this is hardly the case.

This work is the study of a distinguished geographer and that provides confidence that the identification of watercourses as artificial is soundly based. The arguments for their dating are carefully developed. Inevitably, it has relied upon the reading of works of historians or archaeologists for those elements of the analysis. The conclusion to which the interpretations tend provides a challenge for our understanding of the period and it will require a careful evaluation of all the strands of the argument to determine whether the implications of this work are as solid as the text implies.