OFFA’S AND WAT’S DYKES

Offa’s Dyke. King Alfred’s biographer Asser, writing at the end of the ninth century, attributes the building of the great earthwork between Mercia and the Welsh kingdoms to King Offa of Mercia (757–96). It would have appeated more impressive originally when it was probably surmounted by a wooden palisade.

An assessment of Æthelbald and Offa is of their government of Mercia itself and the shortage of charters from the Mercian province is keenly felt. However, some tangible signs do remain of the imposition of the common burdens through which Æthelbald and Offa were able to counteract some of the effects of the introduction of bookland and to establish important principles on the rights of kings to exact public services. Perhaps the most impressive memorials to the kings’ power in Mercia are Offa’s and Wat’s dykes. Attacks from the Welsh became an increasing problem in the eighth century and the solution seems to have been to establish a patrolled frontier along the 150-mile western border of Mercia from the Irish Sea to the Bristol Channel. The defences included at least 80 miles of earthwork defences with a rampart 24 feet high and a six foot ditch and associated forts. Even today the dykes are impressive monuments, but they do not survive in their entirety and may originally have carried stone fortifications on top. Thousands of labourers must have been conscripted from different parts of Mercia to build them and a substantial force would have been needed if the frontier was to be fully patrolled. The Mercian rulers may have been responsible for building other defences as well, such as the earliest phase of the ramparts at Hereford. By the end of his reign Offa was organizing defences against the Vikings in both Mercia and Kent. Jeremy Haslam has suggested that not only was Offa responsible for a defensive network of burhs at important bridgeheads in eastern England, but that he may also have established a series of ‘urban’ markets to stimulate the Mercian economy. Some caution is necessary here for Offa does not seem to have been sufficiently aware on economic matters to encourage the use of coin throughout Mercia or establish Mercian mints. But, even if we do not know as much about Mercian administration as we would like, we can see that Offa, like Charlemagne, had the ability to exact substantial services from his subjects and organize major campaigns of public building works.