The route of a Roman Road in Wiltshire rediscovered?

We have recently been doing some survey work on long barrows near Chettle in Dorset. In this area, the Lidar data shows clear evidence of the Roman road from Badbury Rings to Kingston Deverill, and on to Bath. Whilst reviewing the Lidar a few weeks ago for another purpose, I was distracted by this Roman road and started following it north. This was fairly easy to do until it reached Donhead St Mary, where the trail appeared to go cold. Checking in the Roman Road bible (Margery 1973), plus some other later sources, including the Wiltshire HER, it was clear that the route (named Roman Road 46 – RR46) is unconfirmed all the way the way from Donhead St Mary to Kingston Deverill, with the only confirmed section in the extension to Bath being just south of Bath. How could a road which was so clear in the landscape to the south suddenly disappear at Donhead St Mary? The challenge was on to see if the Lidar gave any clues.

I initially used some of the suggested points along the general route where it is thought traces of the road have been found. This included a useful discussion in a newsletter by the Bath and Counties Archaeological Society. I also thought the road builders might have aimed for a clear gap in the ridge adjacent to the east of East Knoyle, which the modern A350 takes advantage of, but all the lines I extrapolated drew a blank.

Then, by chance, when looking in the area south of East Knoyle, I noticed faint traces of a linear earthwork crossing fields at an oblique angle. This was clearest either side of the A350. To the north west a clear alignment could be seen crossing the woodland labelled on the OS map as Park Coppice, and rising up onto ridge near Wise Lane.

Alignment suggest by Lidar at East Knoyle. Click on image for larger view

Although these traces in the Lidar were looking promising, this was only a short stretch and might not have Roman origins. It would be necessary to trace the alignment over a much longer distance in order to lend weight to an argument for a Roman road. Amazingly, when extrapolating the alignment back towards Donhead St Mary, there are traces at a number of points along an exact straight line for a distance of 5.5km.

At Semley, there are very faint traces of a possible agger either side of the railway which curves across the plot below, with a clearer traces towards the north of the plot. Click on the image for a full resolution image.

Alignment suggest by Lidar at Semley. Click on image for larger view

Finally, north west of Donhead St Mary, there are further traces on the same alignment, shown below:

Alignment suggest by Lidar north west of Donhead St Mary. Click on image for larger view

The following plot shows the complete 5.5km alignment suggested by the Lidar analysis.

5.5km alignment of RR46 suggest by Lidar analysis. Click on image for larger view

Below is a plot showing how this 5.5km alignment fits with the known section of RR46 from Badbury Rings to Donhead St Mary.

Overview of Roman Road 46 (RR46). Solid white line = known alignment, Dashed white line = alignment suggested by Lidar

The existence of this alignment shown in the Lidar does not prove this is the route of the Roman Road. I have been mislead in the past by the routes of pipelines and other infrastructure projects. However, the signs are positive for the following reasons: the straight route, the fact the route is cut by established settlements and roads, suggesting its antiquity and the fact the route assumes the general expected alignment of the Roman road given known sections of road.

The power of the Lidar data to allow such analysis is also clear. Prior to the availability of Lidar data, aerial photos could provide some clues when conditions were right, but in order to look for subtle earthwork traces, researchers would be forced to climb over fences and walls looking for a ploughed out agger crossing a field, with access to private land being a clear problem. With Lidar data, analysis over wide ranging landscapes can be undertaken in a short time, allowing targeted field visits to corroborate clues seen in the Lidar.

The next steps for this research will be to trawl in more detail the available documentary records and maps, and to get out into the field in an attempt to understand the features seen in the Lidar. Also, what is the route of the road north west of East Knoyle, towards Kingston Deverill and Cold Kitchen Hill?

The technique can also be applied to possible Roman roads more local to the Avon Valley. It has been postulated that a Roman road might have connected Old Sarum with the New Forest potteries, perhaps crossing the Avon near Fordingbridge. Also, it is puzzling that the last stretch of Roman Road 45, from the Mendips to Old Sarum, is lost between Grovely Wood and Old Sarum. Could Lidar provide any clues?

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