What did the Romans ever do for us? Well anyone who has seen Monty Python's "Life of Brian" will be aware of the many and varied answers to that question. Law, technology, civilisation, personal hygiene, edible dormice, and so on. But just occasionally you have to ask whether common sense was among their strongest attributes.
This is a question that will have occurred to anyone looking at the north gate at Housesteads Roman Fort, built to the usual format even though there was an almost impassably steep slope immediately beyond it. It is also a question that comes forcefully to mind when visiting Milecastle 48 on Hadrian's Wall, or the Poltross Burn Milecastle as it is more usually know.
The Poltross Burn Milecastle stand immediately to the south of the main Newcastle to Carlisle railway line, which itself passes along the south side of the village of Gilsland. Gilsland no longer has a railway station, but a footpath runs from the south side of the railway, near the Station Inn, and this can be followed steeply down into the valley of the Poltross Burn, and then up steps that climb the far side of the valley to the milecastle itself.
The rules, apparently, said that when the Roman legionaries were building the wall, the milecastles had to be evenly spaced along it, at intervals of one Roman mile. Milecastle 48 was built 1,521m west of Milecastle 47 and 1,458m east of Milecastle 49. Presumably the site of the fort was displaced 30m west from where it "ought" to have been because to have left the spacing regular would have put it in the bottom of the steep sided valley of the Poltross Burn: perhaps even astride the burn itself.
Yet the site chosen remains one that must have caused those based here problems throughout the long operational life of the milecastle. It is on a steep slope that falls away at one corner into the valley to the east, and as a result the entire structure seems crazily tilted. All this could have been avoided by moving the milecastle just another hundred metres or so to the west, but presumably that was more than the surveyor laying out the plan on the ground was prepared to do. After all, he was only here to tell the troops of the Sixth Legion where to build: living and working here once it was built would not be his problem.
Poltross Burn Milecastle can also be accessed from the west, where a car park near the old ruined vicarage serves people wanting to visit the Willowford Wall, Turrets and Bridge. A path runs over fields and across the railway line, before following along its south side to the upper end of the fort.
Poltross Burn Milecastle is, despite the attentions of the railway builders in the 1830s, one of the best preserved milecastles on Hadrian's Wall. It is unusually large, measuring some 18.5m east to west by 21.3m north to south, and there are two ranges of barracks, large enough to house a garrison of some 64 auxiliary troops. The milecastle was traditionally known locally as "The King's Stables", presumably because the remains of the barrack blocks looked like they had once been stables.
Other than the slope of its site and the beauty of its surroundings, the most interesting feature of Poltross Burn Milecastle is a flight of stairs located in the north east corner. It is thought by many that these gave access to a wallwalk around the walls of the milecastle. Only three steps remain, but the geometry of this corner of the structure suggests that the steps would have reached a height of about 4m. Opinions differ as to whether this implies that all milecastles had such wallwalks, and walls of the same height: and there remain arguments about whether a wallwalk around the milecastle would imply the existence (or not) of a wallwalk on the lengths of Hadrian's Wall on either side.