EVEN by modern standards, Offa’s Dyke is a remarkable construction. Yet this ancient earthwork from Chepstow to Prestatyn was built in the Dark Ages – 1,200 years ago.

To walk it is to realise the sheer enormity of the task, carried out with no equipment save the most basic hand tools.

Nothing similar was to be attempted in the British Isles again until the coming of the canals in the 18th century. The dyke consists of a 26ft high earthen bank with a ditch mainly to the west although lying to the east in places.

Archaeological excavations suggest the western side may have been laden with turf to create a near vertical face and that a palisade or wall once existed on its top. Much of it is still traceable for 80 miles from Wye valley to Wrexham.

Not much is known about how the dyke came to be built but it was clearly an attempt by King Offa to place a boundary between his kingdom of Mercia and the Welsh kingdoms to the west.

Offa, king between 757 and 796 AD, was often in conflict with his neighbours and many historians see the dyke as being a defensive earthwork built for his benefit.

Brian White, spokesman for North Wales Ramblers, cites the popular belief that Offa was annoyed by the Welsh raiding his farms and had the dyke constructed to keep his cattle safe. Archaeologist Sir Cyril Fox, who studied Offa’s Dyke in the 1920s and 1930s,saw it as the fruition of an agreement between realms on both sides.

Others have speculated that it might be evidence of a much earlier, prehistoric trackway and possibly the site of a lost Roman wall. Its true length also generates differences of opinion. Historians David Hill and Margaret Worthington argued in a recent book that it never went “sea to sea” and only the 64 miles of more or less unbroken earthwork in the central Marches, (Shropshire, Powys, Wrexham and southern Flintshire) is Offa’s Dyke proper. However, their interpretations are challenged by others.

In 1999, the Clwyd-Powys Archaeological Trust together with Cadw and English Heritage, collaborated on an initiative to help protect the dyke, amid growing concern about erosion. As a result, a conservation officer was appointed to oversee it and remained in post until funding came to an end in 2006.

There has since been no-one else specifically responsible for this scheduled ancient monument thought to have been started in about 785AD.

It took several years to build Offa’s Dyke, yet its role as a border was short-lived. Today, it bears little resemblance to the modern boundary with England. And yet its symbolic importance seems immortal, an enduring bond between Anglo Saxon Britain and the present.