Wall Mile 21 [HB 177–84]
Leaving the major highway north of Dere Street behind us, we head gently downhill towards a rather important little stream, one of the tributaries of the Cor Burn. By the time this reaches the Tyne next to the Roman site at Corbridge, it has been tapped by the aqueduct which supplied the Roman fort and town there and the remains of which are still to be seen on the site. The Vallum is still visible to our right and the Military Road once again on top of the curtain wall. We cross the burn and head up the other side to a plateau which is in fact the fort platform of Halton Chesters (you will find it written as both Haltonchesters and Halton Chesters in the literature), lying partly in the parkland of Halton Castle, further to the south.
Halton Chesters fort (ONNVM) [HB 178–83]
Halton Chesters is 8.8km (5.5 miles) from Chesters and is 2ha (4.8 acres) in area, having been enlarged from 1.7ha (4.3 acres) with a rather unusual western extension south of the curtain wall (making it the only fort on the Wall with an L-shaped plan). Its initial garrison is unknown but it may have been a mixed cohort. The increase in size may be because it later held the ala I Pannoniorum Sabiniana. Once again placed astride the Wall, it – like Chesters – had six gates. A large internal bathhouse was excavated near the western defences, north of the modern road, in the 19th century, with barracks to the east of it. To the south of us, granaries were examined, but most of our knowledge of the site comes from a detailed geophysical survey.
There is nothing to see of the site today beyond the fort platform and a few humps and bumps to the south of the Military Road, whilst to the north the fort is still under the plough.
We leave the fort and enter the pinchiest of pinch points, the Trail being sent along a narrow fenced-off alleyway at the northern edge of the fields, immediately south of the wall bordering the Military Road. We follow this past Halton Red House (to the north of the road) before we emerge, blinking, into the open, grassy (but almost lunar) landscape near Milecastle 21. This area has been much quarried, not only completely removing a short stretch of the Vallum (which, as we are about to find out, is a fine upstanding earthwork just to the east) but also the curtain wall and the milecastle itself, for the Military Road suddenly veers off briefly to the north to skirt round Down Hill.
Milecastle 21 (Down Hill) [HB 177; haiku]
Nothing survives of Milecastle 21 (Down Hill), beyond the suggestion that it ought to have lain somewhere close to where the track meets the Military Road.