When was Hadrian’s Wall built?

He came, he saw, and he built a wall, according to the Historia Augusta (HA). In AD 122, Hadrian (r. 117-138) became only the second serving emperor to visit Britain. We are told that he ‘corrected many abuses and was the first to build a wall, 80 miles in length, which was to separate the barbarians from the Romans’. On the strength of this report in the HA, which was probably compiled more than 200 years after Hadrian’s death, 2022 is the 1,900th anniversary of not only the emperor’s excursion to Britain, but also the order to erect the most famous monument to bear his name. While the traditional start date of 122 is still commonly used – and is also the basis for a welcome series of events commemorating the frontier – specialists are increasingly cautious about where precisely the decision to build the Wall falls amid the events besetting Britain during this era. A different start date could have important implications for how we view the Wall.

What’s in a year?

It is clear that Britain experienced violence at around the time of Hadrian’s visit. The HA notes that ‘the Britons could not be kept under Roman sway’ following Hadrian’s accession. Other straws in the wind include an expeditio Britannica or military taskforce being sent to Britain with 3,000 reinforcements, a tombstone from Vindolanda fort – just south of Hadrian’s Wall – referring to the death of a centurion ‘in war’, and the arrival of a new legion, the VI Victrix. Decades later, a correspondent of the emperor Marcus Aurelius (r. 161-180) used Britain during Hadrian’s reign as an illustration of severe Roman troop losses. That at least some of this turmoil is relevant to understanding the origins of the Wall is indicated by an inscription fragment found reused at Jarrow. The reconstructed text, which may once have graced a victory monument at Wallsend, states that ‘after the barbarians had been dispersed and the province of Britain recovered, he [presumably Hadrian] added a frontier line’.

One of the challenges facing Wall specialists is trying to set these events in chronological order. Perhaps the greatest unknown is the date of the expeditio Britannica. Many years have been proposed, but – as the late Anthony Birley observed – an emperor would normally be personally present. That makes 122 the most likely candidate, because Hadrian was in Britain. On the face of it, this allows a promising scenario to be proposed: the hostilities noted at the beginning of Hadrian’s reign were brought to a close by an expeditio in 122, after which order was restored and the Wall built. This fits nicely with diplomas issued to retiring veterans on 17 July 122. An unprecedentedly large number of military units in Britain discharged troops then, perhaps because terms of service had been extended to quell a preceding crisis. The diplomas also name Aulus Platorius Nepos, the new governor of Britain, who appears on building inscriptions from the Wall. By this reading, the Wall could be a broadly successful expression of Hadrian’s devotion to – as the HA put it – ‘maintaining peace throughout the world.’