Rethinking Offa’s Dyke as a Hydraulic Frontier Work

Howard Williams


Building upon a fresh interpretation of Wat’s Dyke as a component of an early medieval hydraulic frontier zone rather than primarily serving as a symbol of power, a fixed territorial border or a military stop-line (Williams 2021), here, I refine and apply this approach to its longer and better-known neighbour: Offa’s Dyke.  This linear earthwork’s placement, alignments and landscape context are evaluated afresh using a simple but original comparative mapping methodology. First, on the local level, I show that Offa’s Dyke was carefully and strategically positioned to connect, overlook and block a range of watercourses and wetlands at key transverse and parallel crossing points, thus observing and choreographing mobility on multiple axes. Second, I address the regional scale, showing how Offa’s Dyke interacted with, and controlled, biaxial movement through and between water catchments parallel and transverse to the monument’s principal alignments. Both these arguments inform how the Dyke might have operated on the supra-regional scale, ‘from sea to sea’ and also ‘across the sea’, by controlling the estuarine and maritime zones of the Dee Estuary in the north and the Wye/Severn confluence to the south. Integrating military, territorial, socio-economic and ideological functionality and significance, Offa’s Dyke, like its shorter neighbour Wat’s Dyke (in an as-yet uncertain relationship), configured mobilities over land and water via its hydraulic dimensions and interactions. Together, the monuments can be reconsidered as elements of a multi-functional hydraulic frontier zone constructed by one or more rulers of the middle Anglo-Saxon kingdom of Mercia and operative both in times of peace and conflict.


Offa’s Dyke; Wat’s Dyke; assembly place; coast; hydraulics; water; wetland

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Belford, P. 2017. Offa’s Dyke: a line in the landscape, in T. Jenkins and R. Abbiss (eds) Fortress Salopia. Solihull: Helion: 60–81.

Belford, P. 2019. Hidden earthworks: excavation and protection of Offa’s and Wat’s Dykes, Offa’s Dyke Journal 1: 80–95.

Bell, M. 2012. The Archaeology of the Dykes: From the Roman to Offa’s Dyke. Stroud: Amberley.

Bell, M. and Leary, J. 2020. Pathways to past ways: a positive approach to routeways and mobility, Antiquity 94: 1349–1359.

Blair, J. 2007. Introduction, in J. Blair (ed.) Waterways and Canal-Building in Medieval England. Oxford: Oxford University Press: 1–18.

Clarke, P.M. 2020. Early medieval finds from Cheshire reported to the Portable Antiquities Scheme: a survey. Journal of the Chester Archaeological Society 90: 71–122.

Clarke, P.M. 2023. The Early Medieval Material Culture of the Welsh Marches: An Analysis of the PAS Database. PhD Thesis. University of Chester.

Chadwick, A. 2016. ‘The stubborn light of things’. Landscape, relational agency, and linear earthworks in later prehistoric Britain. European Journal of Archaeology 19(2): 245–278.

Delaney, L. 2021. Utilising Lidar survey to locate and evaluate Offa’s Dyke. Offa’s Dyke Journal 3: 83–107.

Edgeworth, M. 2011. Fluid Pasts: An Archaeology of Flow. London: Duckworth.

Fitzpatrick-Matthews, K. 2020. The ‘Wall of Severus’: pseudoarchaeology and the west Mercian dykes. Offa’s Dyke Journal 2: 52–80.

Fox, C. 1955. Offa’s Dyke. A Field Survey of the Western Frontier-Works of Mercia in the Seventh and Eighth Centuries A.D. London: The British Academy/Oxford University Press.

Griffiths, D. 2010. The Vikings of the Irish Sea. Stroud: The History Press.

Grigg, E. 2018. Warfare, Raiding and Defence in Early Medieval Britain. Marlborough: Robert Hale.

Hill, D. 2020. Offa’s and Wat’s Dykes. Offa’s Dyke Journal 2: 141–159.

Hill, D. and Worthington, M. 2003. Offa’s Dyke: History and Guide. Stroud: Tempus.

Malim, T. 2007. The origins and design of linear earthworks in the Welsh Marches, Landscape Enquires, Proceedings of the Clifton Antiquarian Club 8: 13–32.

Malim, T. 2020. Wat’s Dyke and its relationship to Old Oswestry hillfort, in T. Malim and G. Nash (eds) Old Oswestry Hillfort and its Landscape: Ancient Past, Uncertain Future, Oxford: Archaeopress: 145–158.

Malim, T. and Hayes, L. 2008. The date and nature of Wat’s Dyke: a reassessment in the light of recent investigations at Gobowen, Shropshire, in S. Crawford and H. Hamerow (eds) Anglo-Saxon Studies in Archaeology and History 15. Oxford: Oxbow: 147–179.

Murrieta-Flores, P. and Williams, H. 2017. Placing the Pillar of Eliseg: movement, visibility and memory in the early medieval landscape. Medieval Archaeology 61(1): 69–103.

Noble, F. 1983. Offa’s Dyke Reviewed. Oxford: British Archaeological Reports British Series, 114.

Oksanen, E. 2019. Inland Navigation in England and Wales before 1348: GIS Database [data-set]. York: Archaeology Data Service [distributor], viewed 28 September 2022,

Pantos, A. 2004. The location and form of Anglo-Saxon assembly-places, in A. Pantos and S. Semple (eds) Assembly Places and Practices in Medieval Europe. Dublin: Four Courts Press: 155–180.

Ray, K. 2017. Notes Towards a Research Design in 100 Questions, viewed 21 November 2021,

Ray, K. 2020. The discomfort of frontiers: public archaeology and the politics of Offa’s Dyke, in K. Gleave, H. Williams and P. Clarke (eds) Public Archaeologies of Frontiers and Borderlands. Oxford: Archaeopress. 117–147.

Ray, K. 2022. The organisation of the mid–late Anglo-Saxon borderland with Wales. Offa’s Dyke Journal 4: 132–153.

Ray, K. and Bapty, I. 2016. Offa’s Dyke: Landscape and Hegemony in Eighth-Century Britain. Oxford: Windgather Press.

Ray, K., Bailey, R., Copeland, T., Davies, T., Delaney, L., Finch, D., Heaton, N., Hoyle, J. and Maddison, S. 2021. Offa’s Dyke: a continuing journey of discovery. Offa’s Dyke Journal 3: 33–82.

Reynolds, A. 2020. A possible Anglo-Saxon execution cemetery at Werg, Mildenhall (Cvnetio), Wiltshire and the Wessex-Mercia frontier in the age of King Cynewulf, in A. Langlands and R. Lavelle (eds) The Land of the English Kin: Studies in Wessex and Anglo-Saxon England in Honour of Professor Barbara Yorke. Leiden: Brill: 245–275.

Reynolds, A. and Langlands, A. 2006. Social identities on the macro scale: a maximum view of Wansdyke, in W. Davies, G. Halsall, and A. Reynolds (eds) People and Space in the Middle Ages 300–1300, Studies in the Early Middle Ages 15, Turnhout: Brepols: 13–44.

Squatriti, P. 2002. Digging ditches in Early Medieval Europe. Past & Present 175: 11–65.

Squatriti, P. 2004. Offa’s Dyke between nature and culture. Environmental History 9: 9–36.

Swallow, R. 2016. Cheshire castles of the Irish Sea cultural zone. Archaeological Journal 173: 288–341.

Tummuscheit, A. and Witte, F. 2019. The Danevirke: preliminary results of new excavations (2010–2014) at the defensive system in the German-Danish borderland. Offa’s Dyke Journal 1: 114–136.

Tyler, D.J. 2011. Offa’s Dyke: an historiographical appraisal. Journal of Medieval History 37(2): 145–161.

Wileman, J. 2003. The purpose of the dykes: understanding the linear earthworks of early medieval Britain, Landscapes 4(2): 59–66.

Williams, H. 2021. Rethinking Wat’s Dyke: a monument’s flow in a hydraulic frontier zone. Offa’s Dyke Journal 3: 151–182.

Worthington, M. 1997. Wat’s Dyke: an archaeological and historical enigma, Bulletin of the John Rylands University Library of Manchester 79(3): 177–96.

Worthington Hill, M. 2019. Wat’s Dyke: an archaeological and historical enigma. Offa’s Dyke Journal 1: 58–80.



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