Offa's Dyke (Welsh: Clawdd Offa) is a massive linear earthwork, roughly followed by some of the current border between England and Wales. In places, it is up to 65 feet (19.8 m) wide (including its flanking ditch) and 8 feet (2.4 m) high. In the 8th century it formed some kind of delineation between the Anglian kingdom of Mercia and the Welsh kingdom of Powys. Research in recent decades has dispelled many of the earlier theories and ideas about the earthwork.
It is generally accepted that much of the earthwork can be attributed to Offa, King of Mercia from 757 to 796. Its structure is not that of a mutual boundary between the Mercians on the one side and the people of Powys on the other. The earthwork was dug with the displaced soil piled into a bank on the Mercian (eastern) side. Where the earthwork encounters hills, it passes to the west of them, constantly providing an open view from Mercia into Wales. The dyke may have been constructed as a defensive earthwork, as well as a political statement of power and intent.
Offa was one of the great rulers of Anglo-Saxon times, though his reign is often overlooked due to a limitation in source material. That he was able to raise a workforce and resources sufficient to construct such an earthwork as Offa's Dyke is testament to his power. It is likely that some form of 'service' system along the lines of corvée was used to construct the Dyke, with people from certain areas being required to build a certain length of the wall. This can be seen as additional to the normal services that had to be offered to kings. A document exists from around this period known as Tribal Hidage, which makes some assessment of how land was distributed in the 8th century. Though there is little evidence to associate the document with the Dyke, it is possible that both the Dyke and the document stem from a common practice.
Historical evidence 
The late 9th- and early 10th-century writer Asser informed us that "there was in Mercia in fairly recent time a certain vigorous king called Offa, who terrified all the neighbouring kings and provinces around him, and who had a great dyke built between Wales and Mercia from sea to sea" (Asser, Life of Alfred, p. .14). The last four words are vital: historians and archaeologists coming to the Dyke have had Asser in their hand, and have been looking for an earthwork 'from sea to sea'. Sir Cyril Fox completed the first major survey of the Dyke (Fox 1955), and, in agreement with Asser, theorized that the Dyke ran from the estuary of the River Dee in the north to the River Wye in the south (approximately 150 miles, or 240 km). He observed that the dyke was not continuous, and thought it was built only in areas where natural barriers did not already exist.
Frank Stenton, the eminent Anglo-Saxon historian of his day, accepted Fox's description, and wrote the introduction to Fox's account of the Dyke. Though Fox's work has now been to some extent revised, it remains a vital record of stretches of the Dyke that still existed between 1926 and 1928, when his three field surveys took place, but that are now destroyed.
Modern scholarship 
Frank Noble challenged Fox's legacy. His greatest contribution was to stir up new academic interest in Offa's Dyke. His MPhil thesis, "Offa's Dyke Reviewed" (1978), raised several questions. Noble postulated that the gaps in the Dyke were not due to natural features, but that instead a "ridden boundary" operated, perhaps incorporating palisades that left no archaeological trace. Noble also helped establish the Offa's Dyke Association, which maintains the Offa's Dyke Path. This long distance footpath mostly follows the route of the dyke, which is one of the designated British National Trails.
Ongoing research and archaeology on Offa's Dyke has been undertaken for many years by the Extra-Mural department of the University of Manchester. Most recently David Hill and Margaret Worthington have undertaken considerable research on the Dyke. Their work, though far from finished, has demonstrated that there is little evidence for the Dyke's stretching from sea to sea. Rather, they claim that it is a shorter structure stretching from Rushock Hill north of the Herefordshire Plain to Llanfynydd, near Mold, Flintshire, some 64 miles (103 km). According to Hill and Worthington, dykes in the far north and south may have different dates, and though they may be connected with Offa's Dyke, there is as yet no compelling evidence behind this. However, not all experts accept this view.
Alternative theories 
The Roman historian Eutropius in his book, Historiae Romanae Breviarium, written around 369, mentions the Wall of Severus, a structure built by Septimius Severus who was Roman Emperor between 193 and 211:
Novissimum bellum in Britannia habuit, utque receptas provincias omni securitate muniret, vallum per CXXXIII passuum milia a mari ad mare deduxit. Decessit Eboraci admodum senex, imperii anno sexto decimo, mense tertio. Historiae Romanae Breviarium, viii 19.1
He had his most recent war in Britain, and to fortify the conquered provinces with all security, he built a wall for 133 miles from sea to sea. He died at York, a reasonably old man, in the sixteenth year and third month of his reign.
This source is conventionally thought to be referring, in error, to either Hadrian's Wall (73 miles (117 km)) or the Antonine Wall (37 miles (60 km)), which were both much shorter and built in the 2nd century. Recently, some writers have suggested that Eutropius may have been referring to the earthwork later called Offa's Dyke. Most archaeologists reject this theory.
Recent evidence has been found that strengthens the theory of an earlier date for the wall's construction. In December 1999 Shropshire County Council archaeologists uncovered the remains of a hearth or fire on the original ground surface beneath the raised bank of the ancient Wat's Dyke near Oswestry, England. Carbon dating analysis of the burnt charcoal and burnt clay in situ showed it was covered by earth on or around AD 446. Archaeologists concluded that this part of Wat's Dyke, so long thought of as Anglo-Saxon and a mid-8th century contemporary of Offa's Dyke, must have been built 300 years earlier in the post-Roman period in Britain.
The Offa's Dyke Centre 
The Offa's Dyke Centre is a purpose-built information centre in the town of Knighton, situated on Offa's Dyke on the border between England (Shropshire) and Wales (Powys). Some of the best remains of the earthworks can be seen within a two-minute walk from the centre.
Offa's Dyke Path 
The Offa's Dyke Path (Welsh: Llwybr Clawdd Offa) is a long distance footpath close to the Welsh-English border. Opened in 1971, it is one of Britain's longest National Trails, stretching for 283 km (176 mi) from the Severn estuary at Sedbury, near Chepstow, to Prestatyn on the north Wales coast. There is a visitor centre at Prestatyn.
Cultural references 
The Dyke has in some cases been brought into common folklore, though this should not be seen as historical evidence for the purpose behind the Dyke.
|“||[I]t 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.||”|
Today, the England-Wales border still mostly follows the dyke through the Welsh Marches. It has a cultural significance, symbolising the separation between the two, similar to the symbolism of Hadrian's Wall between England and Scotland in the Scottish Marches.
See also 
- England and Wales
- Wales-England border
- Wat's Dyke
- Scots' Dike
- Götavirke (Geatish Dyke)
- Danevirke (Danish Dyke)
- Black Pig's Dyke
- Silesia Walls
- Ian Bapty review of Hill and Worthington, Offa's Dyke: History and Guide, 2003
- Smith, William (1875). Dictionary of Greek and Roman Antiquities. London: John Murray. p. 762.
Eutropius uses the figure cxxxii (132) milia passuum. As a Roman mile ≈1,479 metres (4,852 ft), 132 Roman miles = 195 km (or 121 statute miles); Offa’s Dyke is around 192 km long (a little over 119 statute miles).
- Steve Blake and Scott Lloyd, The Keys To Avalon, Element Books, 2000, ISBN 1-86204-735-9
- CPAT: New book claims that Offa's Dyke is Roman!, article by Ian Bapty
- "What is Offa's Dyke?". The Clwyd-Powys Archaeological Trust. 2009-10-16.
- Matthews, Keith. "Was Offa’s Dyke actually the ‘Wall of Severus’".
- "Latest thinking about OFFA'S and WAT'S DYKES". New Welsh Review 52. 2009-10-16.
- Hannaford, H.R (1999). Archaeological Investigation on Wat's Dyke at Maes-y-Clawdd, Oswestry. Archaeology Service, Shropshire County Council.
"The excavation produced some residual deposits of worn sherds of Roman Samian ware and coarseware pottery. The report suggests that the dyke should be 'regarded as being contemporary with the other great 5th century linear earthwork, the Wansdyke in Wiltshire . . . an achievement of the post-Roman kingdom of the northern Cornovii, rather than a work of 7th-8th century Mercia.' However Dr David Hill, Senior Research Fellow, Centre for Angio-Saxon Studies, University of Manchester ('Offa VersusThe Welsh' - British Archaeoiogy, December 2000) has argued for a date later than the 6th century for Wat's Dyke - that it was constructed as Gwynedd and North Powys briefly became a unified state. Evidence from both dykes suggests, he says, that people were not settling or spending much time in these 'wild zones'."
- "Offa's Dyke Path". Retrieved 6 April 2012.
- Cyril Fox, Offa's Dyke: a Field Survey of the Western Frontier Works of Mercia in the Seventh and Eighth Centuries AD, (London, 1955)
- David Hill and Margaret Worthington, Offa's Dyke: History and Guide, (Stroud, 2003)
- Frank Noble, Offa's Dyke Reviewed, MPhil thesis Open University, (1978). Partly published in Offa's Dyke Reviewed, ed. Margaret Gelling, (Oxford, 1983)
|Wikimedia Commons has media related to: Offa's Dyke|
- Offa's Dyke Association website
- Ramblers' Association: Offa's Dyke Path National Trail
- Clwyd-Powys Archaeological Trust: Introducing Offa's Dyke
- How Offa's Dyke created a genetic barrier between the English and the Welsh BBC Gene Stories article
- Walking Offa's Dyke Path
- History and research Offa's Dyke; English Heritage
- Map of the Offa's Dyke Path in 2 mile sections