The Emperor Hadrian visited Britain, probably in AD 122, and it was under his governor, Aulus Platorius Nepos (AD 122–5/6), that construction began (Figure 1). We know the former fact from Hadrian’s biography (Historia Augusta, Life of Hadrian 11) and the latter from the discovery of a couple of building inscriptions from Milecastle 38 (Hotbank), as well as part of a third from Milecastle 42. We also know that the Wall was constructed and operational by the time it was abandoned in the early AD 140s upon the construction of the Antonine Wall (located further north, on the Forth–Clyde isthmus). Virtually all other dating for the construction of the system within that period of two decades relies upon informed speculation.
Further reading: Breeze and Dobson 2000