Some of its route is followed by the Offa's Dyke Path, a 177-mile (285 km) long-distance footpath that runs between Liverpool Bay in the north and the Severn Estuary in the south.

Although the Dyke has conventionally been dated to the Early Middle Ages of Anglo-Saxon England, research in recent decades – using techniques such as radioactive carbon dating – has challenged the conventional historiography and theories about the earthwork and shows that part was started in the early 5th century, during the sub-Roman period.

The first historians and archaeologists to examine the Dyke seriously compared their conclusions with the late 9th-century writer Asser, who wrote: "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".

Although Fox observed that Offa's Dyke was not a continuous linear structure, he concluded that earthworks were raised in only those areas where natural barriers did not already exist.

Although Fox's work has now been revised to some extent, it still remains a vital record of some stretches of Offa's Dyke that still existed between 1926 and 1928, when his three field surveys took place, but have since been destroyed.

On the Long Mountain near Trelystan, the dyke veers to the east, leaving the fertile slopes in the hands of the Welsh; near Rhiwabon, it was designed to ensure that Cadell ap Brochwel retained possession of the Fortress of Penygadden."

Interviews with Dr David Hill, broadcast in episode 1 of In Search of the Dark Ages (aired in 1979), show support for Noble's idea.

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).

[7] 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.

[13] In December 1999, Shropshire County Council archaeologists uncovered the remains of a hearth or fire on the original ground surface beneath Wat's Dyke near Oswestry.

[17] Further excavations by Clwyd-Powys Archaeological Trust on the Dyke at Chirk Castle found well-preserved remains of the ditch under later parkland; radiocarbon samples were recovered, but the results have not yet been made public.

A 3-mile (4.8 km) section of the Dyke which overlooks Tintern Abbey and includes the Devil's Pulpit near Chepstow is now managed by English Heritage.

All sections of Offa's Dyke that survive as visible earthworks, or as infilled but undeveloped ditch, are designated as a scheduled monument.

[19] Some sections are also defined as Sites of Special Scientific Interest, including stretches within the Lower Wye Valley SSSI and the Highbury Wood National Nature Reserve.

The main professional stakeholders – such as the English and Welsh path and heritage management agencies – are organisationally and functionally separate.

Moreover, despite the lasting legacy of Offa's Dyke for English and Welsh communities alike, there is limited public awareness of the monument and its remarkable link to modern ideas of national identity.The proposal was rejected in 2011.

Opened on 10 July 1971, the Path 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.