A famous ancient earthwork in Britain known as Offa’s Dyke may have to give up its name – it is named after Offa, King of Mercia, due to the belief that it was built during his reign (757 to 796 AD). However, new research has revealed that the dyke may have been built centuries earlier , which sheds new light on the history of the region.

Offa’s Dyke is roughly followed by some of the current border between England and Wales. It is the longest linear earthwork in the UK, and one of the longest in Europe. In places, it is up to 20 metres wide (including its flanking ditch), 2.5 metres high and runs for a staggering 285 kilometres. It is believed that it was constructed to form some kind of delineation between the Anglian kingdom of Mercia and the Welsh Kingdom of Powys, but whether it was intended as an agreed boundary, as a defensive structure with long lost additional fortifications, or for some other use, is not known.

Historians have always associated the dyke with King Offa who ruled the kingdom of Mercia in the 8th Century. But archaeologists have just uncovered evidence that suggests that Offa’s Dyke was built at least 200 years earlier than thought, long before King Offa reigned.

An artist’s depiction of King Offa overseeing the construction of Offa's Dyke. Credit: Mark Taylor .

The discovery was made following excavations on a section of the ancient monument at Chirk near the Shropshire border, where researchers found an ancient layer of re-deposited turf underneath the bank. Samples of the sediment were radiocarbon dated to between 430 and 652 AD, which is the first time the earthwork has been scientifically dated.

"This is a tremendously exciting discovery which means we must re-think some of our assumptions about this important monument", said Paul Belford, director of the Clwyd-Powys Archaeological Trust. "Certainly the dyke was built to make a statement about the power of the kingdom of Mercia."

Despite the new findings, it cannot be completely discounted that Offa had his hand in the massive construction project, as the samples were only taken from one section of the massive earthwork. It is possible that it was not the work of a single ruler but was a long-term project that spanned several centuries.

"Further work is needed on other parts of this enigmatic monument before we can really say who built it and why," said Mr Belford.

Featured image: Offa’s Dyke. Photo source .

By April Holloway