In south-west England, there runs a great earthwork from the mouth of River Dee near Chester, to the estuary of River Severn near Chepstow, traversing through more than 150 miles, although the earthwork is not continuous. This is Offa’s Dyke, and for centuries it has marked the boundary between England and Wales.

Offa was the king of the Anglo-Saxon kingdom of Mercia during the second half of the 8th century. He controlled large swathes of land in the lowlands of Britain to the east and south-east of what was to become England, but the land to the west was divided into a number of kingdoms free from Anglo-Saxon rule. These kingdoms, ruled by the Romano-Britons—a culture that evolved after the fall of the Roman Empire—eventually become Wales.

Photo credit: Andrew/Flickr

The dyke consist of a ditch and a rampart, with the ditch on the Welsh side and the displaced soil piled into a bank on the Mercian side. Throughout its entire length, the dyke constantly provided a commanding view from Mercia into Wales. Wherever possible, natural barriers were utilized and where the earthwork encountered hills or high ground, it passed to the west of them. The dyke was over 20 meters wide and 8 meters high when built, although natural erosion, farming and land development have reduced the height to a mere meter or two.

The construction of the dyke is largely credited to Offa, who sought to define the boundary between his kingdom and the lands of the Welsh. The monumental earthwork—today considered to be Britain's longest ancient monument—was built as a demonstration of the might of the Mercian kingdom, the same way the Hadrian’s Wall and Antonine Wall served to bolster the Roman’s stronghold on the island of Great Britain. The difference is that Hadrian’s Wall and Antonine Wall were built with stone and not earth, and were garrisoned unlike Offa’s dyke that served more as a deterrent rather than fortification.

The 19th century English novelist, George Borrow, in his classic Wild Tales, notes that “it was customary for the English to cut off the ears of every Welshman who was found to the east of the dyke, and for the Welsh to hang every Englishman whom they found to the west of it.”

Borrow had evidently drawn that story from folklore, and tales such as this were invented to signify the Welsh-English enmity and cultural difference that has existed since the creation of the dyke. Offa's Dyke continues to be the frontier between the Welsh and English. The modern England–Wales border still mostly passes within a few miles of the course of Offa's Dyke through the Welsh Marches.

Photo credit: Offa's Dyke Collaboratory