During the early-second century, for the first time in Britain, auxiliary cohorts began to be split into smaller detachments and housed in two (or more) purpose-built encampments. The camp which contained the commanding-officer’s house and the regimental H.Q. are nowadays termed ‘small forts’, while the other type of camp without any administrative buildings are called ‘fortlets’. Small forts were also built to accommodate the officers and men of small auxiliary units called numeri (sing. numerus), and for this reason should be called ‘numerus forts’ in order to avoid confusion. The original Roman terms for all these smaller types of fortification are not known.
The small permanent encampment at Throp was undoubtedly sited here to protect the Stanegate crossing over the Poltross Burn, a tributary stream of the River Irthing which has been identified about 200 yards (180 m) to the east (NY 6334 6591). The camp may be classed as either a small fort or a fortlet, but opinion favours the latter possibility, with the fortlet here perhaps housing the other half of the force whose headquarters and administration staff were garrisoned at the contemporary small fort at Haltwhistle Burn.
Partly excavated by the Cumberland and Westmorland Antiquarian & Archaeological Society under F.G. Simpson in 1910 and reported in the Society Transactions of 1913, this small fort is perfectly square, measuring 180 feet (55 m) internally and enclosing an area of about ¾-acre (0.3 ha). The fort was defended by a turf rampart set upon a base of stones and fronted by a single ditch; the earthwork remains of these defenses have been much reduced by ploughing over the years but still survive to a maximum height of about 2½ feet (c. 0.7 m). Pottery recovered from the fort’s interior show an original occupation period contemporary with the construction of Hadrian’s Wall, followed by a second brief occupation during the 4th century. Even though several blocks of stone had been reputedly ploughed up at the site prior to the excavation no traces of stone buildings were found, not even of robber-trenches, unlike the contemporary fort at Haltwhistle where all internal buildings were of stone construction.
References for Throp Fortlet
- Hadrian’s Wall from the air by G.D.B. Jones & D.J. Woolliscroft (Tempus Stroud, 2001);
Map References for Throp Fortlet
NGRef: NY630657 OSMap: LR86