Hadrian's Wall was a Roman frontier work of the early 2nd cent. running 70 miles from the Tyne near Newcastle to the Solway west of Carlisle. Commenced at the behest of Hadrian on his visit to Britain in 122, the wall was originally to consist of a running barrier fronted by a ditch (except on the crags of the central sector), with a gateway defended by a fortlet every mile (milecastle) and two watchtowers (turrets) between each pair of milecastles. The troops remained based in forts along the Tyne–Solway road, the Stanegate. The eastern three-fifths of the wall were in stone, the western two-fifths in turf, later rebuilt in stone. With the construction of the wall well advanced, the decision was taken to place the garrison forts actually on the line of the wall and to extend the eastern terminal from Newcastle to Wallsend. The final addition was the ‘vallum’ to the rear of the wall, a ditch flanked by two mounds with causeways only at the forts. The western terminal of the wall was at Bowness-on-Solway, but fortlets (milefortlets) and watchtowers (towers) continued down the Cumberland coast. The entire complex was built by the three legions in Britain, though garrisoned by the more mobile auxiliary troops. Apparently a frontier, it was designed to be permeable, to supervise not to deny movement. The line could not have been held against a concerted attack; in the event of a crossing Roman forces would concentrate to the south to expel invaders. North of the wall were further forts monitoring Northumberland and the Lowlands. The psychological and propaganda effect of this enormous feat of construction and of the garrison along it must have been immense, not to mention the demographic and economic impact of the thousands of troops stationed along its line.

Alan Simon Esmonde Cleary

Hadrian's Wall Defensive fortification in n England, Erected (ad 122–36) on the orders of Roman Emperor Hadrian. It extended 118.3km (73.5mi), and was about 2.3m (7.5ft) thick and 1.8–4.6m (6–15ft) high. Forts were built along its length. Extensive stretches of the wall survive.