rampart. For a wall is made of stones, but a rampart, with which camps are fortified to repel the assaults of enemies, is made of sods, cut out of the earth, and raised high above the ground, like a wall, having in front of it the trench whence the sods were taken, with strong stakes of wood fixed above it. Thus Severus drew a great trench and strong rampart, fortified with several towers, from sea to sea. Bede’s Ecclesiastical History of England, Bk 1-5 However, the solution to the problem lies a few chapters later in Bede's account. In Book One Chapter Twelve of Bede's Ecclesiastical History, he writes that the Romans "built a strong wall of stone directly from sea to sea in a straight line between the towns that had been built as strong-points, where Severus had built his earthwork ... straight from east to west". The strong wall of stone cannot refer to the Antonine Wall or Offa's Dyke, so it clearly refers to Hadrian's Wall, especially as Offa's Dyke runs from north to south. Also, as Severus's earthwork is described as being in the same location as Hadrian's Wall, it cannot be Offa's Dyke either, so the earth rampart with a great trench that Bede refers to must be the Vallum, the adjoining earthen barrier immediately south of Hadrian's Wall. Where Bede got it wrong was in attributing the Vallum to Septimius Severus, and saying that it predated the Wall. In fact the Vallum was the work of Hadrian, and slightly post-dated the Wall. Evidence has also been found that challenges the accepted date of the construction of Offa's Dyke. 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. 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 2014, excavations by the Clwyd-Powys Archaeological Trust focused on nine samples of the Dyke near Chirk. Radiocarbon dating of redeposited turf resulted in a series of dates. In one section, these ranged from AD 430 to AD 652 and in another section from AD 887