Offa's Dyke and Wat's Dyke are 2 dykes that sit along the border between Wales and England. Yes they are not hillforts, but I am doing a page on them. Scotland and England have Hadrian's Wall as the famous nickname for The border, though really though it had similar geographic and political reasons for why it occurred, as the boundary between Scotland and England, it did not really have much to do with the real border between Scotland and England. Meanwhile Offa's Dyke, which is less used as shorthand for this border, actually played a huge part in the differentiation of these 2 realms. 

So the main Offa's Dyke is one that runs from the southern reaches of Shropshire to North East Wales, and Cheshire. Up in the North East there is also Wat's Dyke, which runs past places such as Wrexham and Holywell. The remnants of both dykes still survive on portions of the border area. 

To the south of these dykes, it is more the rivers, and hills that separate as the boundary between Wales and England. Indeed in west Herefordshire, there is a area called Archenfield, which was a Anglified version of the Dark Ages Welsh kingdom's name Ergyng. This area was a one that there was debate over whether it was in Wales or England to the 16th Century act of union, and it was mostly Welsh speaking to the 18th Century, and partly to the 19th, unlike east Herefordshire.  

It  seems best to say that Offa's Dyke was built by the  Saxon king Offa, so as to confirm or establish Saxon moves up to where Wales is, in the late 8th Century. This was not that long after some more of western midland of England had been taken into the Saxon fold. This had been a tactic of Saxon kingdoms such as against rival Saxon kingdoms, but more so against groups of the Britons. For instance dykes appear in Western England, around the time Glastonbury was taken, and this before the move west forcing the West Britons, to just have Cornwall, before it became a duchy of England. So it is fair to say, despite how some of dykes looks pretty impressive and intimidating as a barrier, from a distance, that it was really a marker of territory. 

The most astonishing aspect of this, is how the language boundary in many places kept quite much so with this boundary to the 16th and even in cases the 19th Century. Surely what must have occurred is the Saxon language became the language for both Saxon settlers, and absorbed British or Olde Welsh speaking locals, while west of it, the Welsh language remained, for what were differently ran areas. So for instance a few very small places that had been regarded as part of Wales were placed in English counties after the act of union, despite being west of the dyke, and these places were still Welsh speaking at that time. Places such as Llanfair Waterdine, and such, where I walked from when I went up to the dyke on the Shropshire hills. It is amazing, how many Welsh names are in that parish, and how some of the English names are gobbledygook transliterations of meaningful Welsh names. Maybe indicating what happened in the Saxon conquest of England. 

Meanwhile at Oswestry, those places west of the dyke, like at Selattyn, a place in Shropshire, with a Welsh name, remained partly Welsh speaking to the 19th Century. English expanded across Wales at different speeds, for most of Wales the big change occurred from the 19th Century, some portions had been English speaking even before the 16th Century as of some English towns, even though some of those towns had become Welsh speaking overtime, but parts of east Powys were moving towards English even before the 18th Century. 

Wat's Dyke again, is a fine site, and parts remain in Holywell. I notice it is on a elements of a cusp of a hill in some parts. It was likely built just after Offa's Dyke, and is in parts parallel, so indicates changing Saxon tactics, or territory.  

In the later Dark Ages, the Saxons had been moving villages deeper into the North Wales coast, such as at Rhuddlan. This could help explain a other dyke, from Whitford to Trelawnyd, so more west east, in North East Wales, it runs parallel, to the coast, just south of the Halkyn hills, that is right on the edge of the North East Wales coast. The Whitford Dyke, this dyke had little effect on the language, as Gwynedd's kingdoms were retaking lands for Wales as time went on. I have seen slight indentations and lines in fields east of Trelawnyd indicating that, but there is nowhere as deep as some of what occurs on the other 2 mentioned more famous dykes for this page though. Perhaps indicating it was less important, and protected. So as of that fact it was not as long lasting, North East Wales stayed Welsh speaking for the most part to the 19th Century.

Much of dykes today have been denuded. There are parts where housing has bitten into some of it, and parts where they sit right by it, which is why so places have the name of these dykes in their streets. Some bits have been swallowed by railway lines. 

The Offa's Dyke path seems to actually mostly not go on the Offa's Dyke, as in the south it is not there, and in the north it cuts west up the  Clwydian hills, which with their hillforts may have served a similar purpose in times past for some groups. It is a great path though, and if it went along the dyke in the north, it would have to follow railways lines, and housing estates, which is less of what hiking is supposed to be about, as in seeing the great outdoors. I mean you can go on a walk in a estate if you want, but the trail is more about nature. 

I have seen some small, low remains at places near Llangollen, east of it, that are of interest. Then though in Clun in South West Shropshire the dyke has areas that really can bring the imagination about rival armies on other side, or boundaries marked. The beautiful lands of Wales to the west and England to the east, it looks a impressive sight, Specially as you see cattle up there, and in those days protecting cattle from raiders would be key for a economy. I have some pictures of it on this page, I have Clun's Shropshire Hills, above, then a Llangollen, and then Holywell's Wat's Dyke images, and you need my permission to use those pics. As I say I am no expert on this subject.