The lowland route taken by the early 9th-century linear earthwork Wat’s Dyke leaves few places where it is well preserved. This contrasts with the better preservation of its longer and earlier (late 8th century) counterpart, Offa’s Dyke, which navigates higher terrain to the west. This appearance is deceptive: where well-preserved, and/or where survey and excavations have taken place, the bank and ditch of Wat’s Dyke can reach a comparable scale to more monumental sections of Offa’s Dyke. A short walk from Erddig Hall will take you to one such place.

Unbeknownst to most visitors to the National Trust property at Erddig, one drives across the line of Wat’s Dyke just south of Erddig Hall. I say this since the heritage interpretation of the Hall, its gardens and park obliterate this important 9th-century monument from all recognition. Just as Wat’s Dyke is obscured and mis-dated on the fairly new signboard in the woods north of the hall at Erdigg Castle (a Norman motte-and-bailey), the information in the park to the south doesn’t so much as mention Wat’s Dyke.

Where’s Wat’s Dyke?

So imagine you are visiting Erddig NT property. Having driven across the Black Brook on a small bridge, the road rises and turns sharply left by the house Bryn Goleu. At this point you are driving over the Dyke and then parallel to it northwards as you approach the Hall. The Dyke is running along the top of a steep scarp above and overlooking the Black Brook. For much of this length, the Dyke has been levelled by post-medieval activity associated with Erddig Park.

The line of Wat’s Dyke, now largely obliterated, in Erddig Park. Looking south, the approach road to the Hall is on the left, running parallel to the Dyke.

However, at The Rookery, just north of where the road crosses it, the Dyke looks very different: it is monumental in scale. As in Erddig Wood, it has a well-preserved bank, ditch and counterscarp bank before the ground falls steeply away westwards toward the Black Brook. The Dyke also behaves differently here; because it is carefully following the line of this scarp, its line is described by Fox as ‘sinuous’  from Erddig Castle south to The Rookery. In contrast, south of  it runs relatively straight across level ground southwards towards Middle Sontley.

The surviving section at The Rookery is therefore important, not only because of its scale of preservation, but because the Dyke here projects westwards significantly to take in a promontory of higher ground above the river. Also, rather than ‘sinuous’ as Fox describes it, I think it adopts the ‘adjusted-segmented’ style that Offa’s Dyke does when subtly shifting its alignment in response to the topography: an observation made first by Keith Ray about the older monument but seemingly not conclusively identified yet for Wat’s Dyke. In other words, the Dyke never curves: it runs in short straight sections that adjust in subtle fashions in response to the topography. Offa’s Dyke does this, and so does Hadrian’s Wall many centuries older than both these Mercian frontierworks.

Looking west over the ditch to the counterscarp bank
Looking south as the Dyke navigates the edge of the promontory above the Black Brook (to the right just out of shot)
Looking south, one can see the huge bank (left) and ditch (right)
looking north along the line of the Dyke with its bank on the right
Looking north-east up from the bank of the Black Brook to see the Dyke bending westwards to take in the promontory.

Only part of Wat’s Dyke at The Rookery open to public access: the rest is in the garden of Bryn Goleu and in inaccessible fields.

This section is given attention in Sir Cyril Fox’s survey. He recorded a profile of the monument here (Fig. 115, Profile X) where it is surviving to an impressive scale. Meanwhile his photograph – Plate XLIIb – is captioned describing it as an ‘untouched portion’.

Is the exceptional monumentality here the result of Erddig Park affording it extra/different protection? Or was this section originally more monumental than elsewhere? These questions are difficult to answer, but I would say that the particular attention the monument plays to following the scarp in an sinuous way in the section between the confluence of the Clywedog and the Black Brook below Norman Erddig’s motte-and-bailey and the confluence of the Glanyrafon Brook and the Black Brook is hardly likely to be coincidental. Further south of here, the Dyke is happy to set itself back from the Black Brook but run parallel to it on the higher ground. Yet in this short section between the two confluences, the Dyke carefully follows and overlooks the Black Brook. Hence, the projection of the Dyke westwards to take in the small promontory of The Rookery overlooking the Glanyrafon and Black confluence reveals the strategic importance of the confluence. Perhaps the two confluences, and the area in between was an important confluence of land routes too. As such it was an imperative for the Dyke to control this crossing point for human and animal traffic moving west-east as well as north-south.  This is illustrated clearly on the annotated screen shot from GoogleEarth below: the water course marked in blue, a crude indication of the line of the Dyke marked out in red. The scale and careful adjustments to the line of Wat’s Dyke at The Rookery therefore reveal the strategic importance for the Dyke of controlling a confluence; facing off against those approaching along these streams from the west.