CPAT have just completed a fabulous 2-week dig funded by the National Trust and Cadw, and supported by volunteer diggers (including University of Chester students), in the Chirk Castle Estate (Chirk, Wrexham). As well as opening trenches near the castle itself, they have been investigating a hitherto completely denuded section of the famous eighth-century AD linear earthwork: Offa’s Dyke to the north of the castle. The dig is summed up by an article (including a fab video) in The Leader (note: there are a few typos in the article: “Cadwr” = Cadw, “Offah’s” = Offa’s and “Erdigg” = Erddig). 

The Offa’s Dyke Collaboratory visited the dig in its early stages two weeks ago, as part of the Offa’s Dyke Conference. Following this link for details of the event and visit. Returning to the site at the end of the dig, I was privileged to see the final state of the CPAT trench. I defer to CPAT themselves to disseminate the results in due course. However, with the permission of Ian Grant, I share some preliminary thoughts on what are truly monumental results. On a personal note, it is the first time I’ve had the opportunity to see first-hand what relatively very few archaeologists have seen: a completely excavated section of Offa’s Dyke’s ditch!


The results astounded me and photographs struggle to convey the monumental scale of the ditch of Offa’s Dyke that CPAT revealed. Ian and his team of experienced archaeologists and volunteers did not simply follow the ditch-cut’s sloping angle and presume they’d reached the bottom at just over 2m. Instead, Ian’s archaeological experience paid off and he followed the ditch as its cut a distinct sharp-angled slot down another entire metre!

Just let that sink in: Offa’s Dyke has just been shown to have had a whopping 5-6m wide and 3m-deep ditch near Chirk Castle! This ditch has completely disappeared over the centuries, and particularly during post-medieval landscaping, just as the bank itself is heavily denuded at this point and might have originally been over 2m high (based on comparisons with other excavations (Ray and Bapty 2016: 186). Offa’s Dyke’s bank and ditch – notwithstanding any pallisade or other features that defined the original construction, has been revealed in this section at least to have been a truly monumental barrier to be reckoned with. Completely lost at this point until the CPAT dig, the rediscovery and scale of the dyke are phenomenal.

Charcoal samples from the ditch might assist with further dating of the dyke and its immediate post-construction filling. Moreover, further work on Offa’s Dyke at Chirk Castle is urgently needed in future years to ascertain the character of the heavily denuded bank material – surviving in only a fraction of a metre of material where the bank was, and in a mixture of material, including some large stones that might have formed part of a revetment, slumped into the ditch. Further work is also needed to ascertain the presence and character of quarry ditches to the east of the bank, and any counter-scarp bank to the west of the ditch. For now, I simply want to celebrate these excellent results, mirroring what CPAT achieved earlier this summer in relocating Wat’s Dyke just south of Erddig Hall.


A bit of context

Keith Ray and Ian Bapty’s recent book reviews published evidence from surveys excavations for the scale and character of Offa’s Dyke ditch. They question the statement that Offa’s Dyke is usually 2m deep (by Hill and Worthington 2003) and cite Mainstone (Shropshire) and Redwood Lodge, Buttington (Powys) as excavations showing a 3m deep ditch combined with a varying width of between 6m and 9m. Elsewhere at Orseddwen, south of Selattyn Hill, it was suggested that the ditch was only 3m wide and 1m deep. In the accompanying notes, Ray and Bapty query whether the ditch was fully bottomed at these locations. It is important to note that this isn’t simply an issue of archaeologists not identifying the depth of the cut, but identifying the location of the ditch itself. Given bank material might slump into the ditch differentially on the west side of the ditch, encourages the possibility that an unbottomed excavation would misidentify a later slump line as the ditch profile, but also misplace the ditch west of its actual line. To my eye, such a situation of horizontal shift in the bottom of the slump lines occurs in the top of CPAT’s section at Chirk Castle. A further distraction are later ditches that look like a ditch for the dyke, but are instead later recuts for land-drainage purposes as at Bronwylfa Road, Esclusham, Wrexham (Ray and Bapty 2016: 181). Such factors can distract archaeologists, especially when dealing with a ditch on such a truly gigantic scale.

Ray and Bapty then turn to the evidence from Ffrydd Road, Knighton which indicates an 8.5-9m wide and 3m-deep ditch at one point, but only 4m wide and yet still a consistent 3m deep ditch at another. Significantly, a slot at the base was identified, and one wonders if this was fully bottomed out given the depth of the slot identified at Chirk. Moreover, the Chirk evidence confirms Ray and Bapty’s argument that, the ‘most common as-dug ditch-profile appears to be a V-shape’ (Ray and Bapty 2016: 182), but raises concerns about whether a slot has been missed by some previous excavations.

Notwithstanding the validity of Ray and Bapty’s concluding point that a ‘suite of build practices was brought into effect that complemented the suit of placement practices’ (Ray and Bapty 2016: 184), the Chirk evidence might well suggest that Offa’s Dyke, outside of situations where the dyke sat at the top of steep slopes where a shallow ‘notch’ might suffice for a ditch, might have been of varying width but a relatively uniform 3m in depth. Further work is clearly needed to ensure ditch-cuts are followed to conclusive bottoms in order to reveal the full monumental breadth and depth of Offa’s Dyke as suggested by the Chirk evidence.


Incidentally, the dyke is still visible above the level of the nearby lake, as previously posted.



I took some brief photographs myself with the permission of the archaeologist in charge – Ian Grant – and I’m grateful to Fiona Grant for the permission to share the low-resolution photographs above.


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