Offa’s Dyke was named after the English king believed to have ordered its construction to keep out Welsh rivals.
Now new research suggests that it was built at least a century earlier.
Offa was King of Mercia (today’s Midlands area) from 757 to 796. He was a very powerful ruler and established his reign beyond the boundaries of Mercia, eventually controlling most of southern England and East Anglia.
Offa’s Dyke is an Anglo-Saxon earthwork which formed the border between England and Wales. It is composed of a mount of up to 8 ft high on the English side and a ditch on the Welsh.
Stretching 177 miles, it is the longest in the UK.
Radiocarbon dating was used on parts of the structure and the results indicated that it was built no later than the middle of seventh century.
Experts have described it as a “tremendously exciting discovery” as it is the first time accurate scientific dates have been clarified.
The carbon dating process revealed a 95% likelihood that the earthwork at Chirk was built between 430 and 652. That period covered the reigns of several Mercian monarchs, including Creoda (reigned from 584-593), who established a Mercian capital at Tamworth, and Penda (626-655), whose reign saw the start of a period of ascendancy over other Anglo-Saxon rivals known as the Mercian Supremacy.
Although it had been built earlier than scientists had anticipated, the structure was still most probably built as a defence as well as a statement of power.