The ditch is always present to the north of the curtain wall, except where the crags in the central sector make it unnecessary. Unlike the flat-bottomed Vallum ditch, the Wall ditch was originally V-shaped in Section.
Hare Hill ditch
At Banks Turret, the road, which used to follow the line of the curtain wall closely, originally ran over the top of it, but has subsequently been moved onto the berm, whilst the ditch is very plain to the north of the road.
The ditch east of the Poltross Burn
Crossing the Poltross Burn next to the lofty viaduct, we climb up a footpath then turn right through a kissing gate and emerge on top of a hill. Looking downhill, to the west, we can clearly see the course of the ditch and, to the south of it, the line of the curtain wall indicated by the property boundary at the end of the terrace gardens. Here is another good place to study how the Roman army used the terrain to their advantage when laying out the ditch, for here it is set back to the south of a prominent natural north–south slope, thus forcing an attacker to run uphill before attempting to cross it.
Ditch east of Gilsland
East of Gilsland, it is possible to walk along one of the finest – possibly even breathtaking (if you are inclined to having your breath taken) – sections of Wall ditch. As you survey it, remember that we are not standing at the original base, since sedimentation ensured that, however often it was cleared out, material would rapidly accumulate at the bottom. Once again, the ditch is cut into a foreslope, with the northern lip – enhanced by the ditch upcast – making it even more pronounced and a substantial obstacle to the would-be attacker. The line of the curtain wall is, naturally, indicated by a property boundary wall.
Ditch near Chapel House
The ditch becomes more pronounced, recalling that fine stretch on the eastern edge of Gilsland, near the position of Milecastle 47 and at the point where the Trail crosses a field wall by means of a ladder stile.
A substantial length of ditch runs up the hill just east of Thirlwall Castle and the Trail affords the slightly dubious opportunity to walk along the rather irregular upcast mound. The view across Gilsland, nestling in the valley of the Irthing, towards Birdoswald are worth the effort getting there (easy from Walltown Quarry car park, less so from Thirlwall view car park).
Ditch between Great Chesters and Cawfields quarry
Because it is hidden to the north of the field wall, the ditch here is often missed by walkers, but it is worth peering over the wall at it to remind ourselves that it is needed to cover this long section with no crags.
Lodhams Slack ditch
A substantial gap to the west of Winshield Crags, Lodhams Slack, is covered by a traverse of ditch between the crags. The curtain wall is skulking beneath a modern field wall rather shamefacedly, given the spectacular nature of its surroundings.
Ditch (between Crag Lough and Milecastle 38)
To the east of Crag Lough, the ditch has been inserted across Milking Gap between Turret 38a and Milecastle 38 to counter the absence of the defensive value of the crags along here once again. The gap was too broad to need a re-entrant. Crossing the access road to Hotbank Farm, we can clearly see the ditch ahead of us with the modern stone wall on top of the remains of the Roman wall before we pass through the kissing gate to take us to the south side of the curtain wall again.
Ditch in Busy Gap
The curtain wall, beneath the by-now-familiar field wall, descends into Busy Gap and is breached by a modern gateway called the King’s Wicket which seems to have a history. Busy Gap was a traditional route through the wall in the medieval and post-medieval period, ne’er-do-wells who used it for their nefarious activities earning the nickname Busy Gap Rogues (a term of abuse that remained in use into the 19th century). It has an even older significance, however, as an earthwork dyke that may date as far back as the Bronze Age runs through the gap and on towards what is now Scotland. Once again, the Roman Wall merrily slices across a traditional landscape. The angle between the wall and the dyke is adapted into a triangular enclosure by the earthwork known as Black Dyke, here thought to be used as a post-medieval stock enclosure associated with the passage through the wall. The Wall ditch reappears across Busy Gap, recognising its tactical vulnerability but terminates again once it begins to ascend Sewingshields Crags.
Ditch and Vallum between Carrawburgh and Limestone Corner
Departing Carrawburgh, we head eastwards up the field, past some recent quarrying next to the Military Road, and before long the Vallum re-emerges, now with the Military Way perched on its north mound. We now have to negotiate another crossing of the Military Road (so, once again, take care as there are maniacs in cars along here), backtracking slightly to get into the far field and resume the Trail to the north of the ditch. Before heading on, look back towards Carrawburgh and you will see a view that has changed little from when J. P. Gibson took a photograph of it before the First World War, although his model was then able to sit down in the road (which did not have a tarmac surface and was much lower than the current ‘blacktop’).
We plod on to the north of the ditch, now being a good time to admire those roadside drystone walls (they are easier to see from either side than from the road, due to the changes in level since the road was built). The larger blocks, curiously familiar from our perambulations next to the curtain wall, are interrupted by regular lines of throughstones. This pattern of construction becomes obvious when poor quality repairs are attempted in places, although this stretch is in good order.
Limestone Corner is one of the great enigmas of Hadrian’s Wall. Why an enigma? Well, there’s no limestone there for starters; it starts further to the east – no matter. More perplexingly, this is the point at which the Roman army got fed up digging their ditch and gave up. It is perplexing as the Vallum diggers had no such problems and ploughed through the whin stone along here regardless, so it seems the ditch-diggers may have had a bad Friday afternoon. The most exciting thing about Limestone Corner is that the course of the ditch (and curtain wall) moves offline in order to stay at the top of the scarp, thereby (once again) enhancing the defensive effect of the ditch (although not quite as much as if they had actually finished it, of course). To the south of us, large chunks of whin have been discarded down the slope, the largest of which (subsequently split into two) has been estimated as weighing around twelve tonnes (naturally, there is no record of anybody having actually weighed it; this is a guesstimate). East of the dramatic and slightly forlorn pinnacle of rock, we find that the ditch gets ever shallower, evidently having been little more than marked out, rather than fully excavated.
East of Heavenfield and west of Stanley Plantation
The Trail follows a fine section of ditch east of Heavenfield, immediately north of the Military Road, the southern carriageway of which rests on the line of the curtain wall, whilst the berm is beneath the northern half of the road. There are areas where the upcast mound is clearly visible north of the ditch, but even more spectacularly the ditch occasionally uses the advantage of the natural northwards slope to great effect.
East Wallhouses ditch and Vallum
Stretches of the ditch are visible to either side of the road to Moorhouse (the Trail goes along the north lip of the ditch in each case) whilst the Vallum is visible as an earthwork in the fields to the south.