Offa's Dyke is an amazing 129 kilometre earthwork. Twelve miles longer than Hadrian's Wall it is Britain's longest ancient monument. As it follows the English-Welsh border, from Chepstow in Gloucester to Prestatyn in North Wales, it passes through many Areas of Outstanding Natural Beauty and National Parks including the Black Mountains, and the Brecon Beacons. In Gloucestershire alone, the Dyke offers a dramatic view over the Wye Valley and a particularly easily accessible section of the Dyke can be found at Devil's Pulpit, near to Tintern Abbey. But there is more to Offa's Dyke than breathtakingly beautiful scenery. Offa's Dyke is a lasting testament to the strong government of England's first real King - King Offa.
King Offa was the twelfth King of Mercia. The Kingdom of Mercia was founded in the late 6th Century by King Creoda, an Anglo-Saxon from Angeln in South West Denmark. Mercia, which means 'Land of the Border People' comprised of most of the midland counties of England. The Mercian Kings chose to rule their Kingdom from Gloucestershire, they lived in Tamworth and Gloucester and were buried in St Oswald's Priory in Gloucester - the remains of which can be seen in Archdeacon Street Park.
Offa came to the throne in 755AD and was at once determined to expand his country. Between 771 and 779 he declared war on Kent, successfully defended his border lands with Wales, defeated King Cynewulf of Wessex and annexed the Welsh Marchlands. Then just two years before his own death in 796, he murdered King Ethelbert of the East Angles to take possession of East Anglia. In addition to his military conquests, he gained alliances with Wessex and Northumbria by marrying two of his daughters to their Kings.
His tactics were successful. Mercia under King Offa comprised of most of what we now call England. He controlled all the lands from the Rivers Mersey and Trent in the North, to the River Thames in the South, from the Fens in the East to the Welsh borders in the West, and also Lindsay (Lincoln), East Anglia and Kent. It can be said, therefore, that Offa was the first King of England; such was the size of his Kingdom.
Offa was known on the international stage as well. As well as dealing with the Papacy, he was also a friend of Charlemagne, the Holy Roman Emperor, who ruled from Francia. To enable trade between the two kingdoms, Offa established the penny as the standard monetary unit in Mercia and ensured that the silver content of his coins was identical to that used in Francia.
As to why he decided to build Offa's Dyke, no-one can be entirely sure. The first written reference to the Dyke was made in the 9th Century by a Welsh scholar named Asser. He wrote that a king named Offa, "had a great dyke built between Wales and Mercia from sea to sea."
Most archaeologists believe that the Dyke was built as a result of problems with the Welsh princes of Powys - probably as a result of the annexation of the Welsh Marchlands in 779. They believe that the Dyke was built as a clear indicator of the border and its height meant it could be used defensively, to watch out for invaders from Wales.
Sir Cyril Fox, however, an archaeologist working in the 1920's and 1930's, believed that the Dyke was the result of collaboration between Mercia and Wales. He put this theory forward because at the time of its construction, there would have been Welsh and Mercian settlements either side of the Dyke. Even today the remaining 129 kilometres of the Dyke cross the border nine times.
This theory has, however, been subsequently quashed by more recent excavations, which emphasise the defensive nature of the structure. It has been discovered, for example, that when it was first built, the western side, i.e. the side facing Wales, was fixed with turf which created an almost vertical face, which would, therefore, have been difficult to climb.
For whatever reason it was built, the construction began around 780AD and the Dyke is believed to have been completed within a decade. The Dyke used naturally occurring barriers where they could be found and where there were no such barriers, an earth bank was constructed instead. Upon completion it ran for 240 Kilometres and in some points the Dyke was four hundred metres above sea level. At eight metres high when it was first constructed and with a twenty metre wide ditch to the west of it, it would have taken thousands of men to construct the Dyke and that would have required a lot of organisation. For many kilometres it runs in an absolutely straight line - no mean technological feat for the Dark Ages. This leads to us question how 'dark' the Dark Ages really were. Under Offa there certainly seems to have been a cohesive system of government to enable him to build this Dyke in so short a time frame.
But the Dyke's usefulness as a defensive feature was short lived too; most archaeologists agree that Offa's Dyke fell out of use within a few years of its construction. Over the following centuries many parts of the Dyke were reclaimed as farming land, but its original purpose was not forgotten and Offa's Dyke has had a permanent effect on the English and Welsh ideas of nationality, separating Wales from the rest of England.
The Offa's Dyke Path National Trail, which visitors can follow today, was opened in 1971. It follows the original Dyke as much as possible, but where the Dyke climbs into inaccessible stretches, such as the Black Mountains, the Path follows a scenic, more accessible route as close as possible to the Dyke.
So if you want unrivalled views of England and Wales, a chance to walk in the footsteps of our Anglo-Saxon ancestors, and the opportunity to marvel at the achievements of a dark ages King, then you must visit Offa's Dyke.