I wrote something earlier in the year about a potential Roman fort on the Killerton Estate near Exeter, Devon.
In 1984, an aerial photograph had shown a triple-ditched ‘playing card’ shaped enclosure which looked like the plan of a typical Roman fort.
A group of us had walked across a neighbouring ploughed field and found no Roman finds.. but we resolved to reconvene in August and test the site with our National Trust geophysical survey equipment.
Here are the results of our three day investigation. Dave with his Fluxgate Gradiometer and Fi with the Killerton NT Heritage Archaeological Ranger Team (HART), wielding the Earth Resistance Meter.
The site lies under a huge grass field which is cut on the east by the M5 motorway and on the south side by a deep quarry.
We made our baseline the row of telegraph poles that crossed the field. The pole in the middle became our zero point and from there we marked out the 20m grid and began walking up and down with our machines.
After a while, Dave reported extremely high readings across the middle of the site and we wondered why a helicopter hovered over us. On the second day a British Gas official climbed through a hedge and asked what we were doing. Apparently an important gas main runs through the field and is constantly monitored to prevent intrusive activity which might disrupt the supply.
I reassured him that we were not going to excavate the site and then asked whether any archaeological recording was done when the pipeline was constructed through the field. Too long ago for such annoying things to be considered it seemed and he left us with a leaflet.
Derek reached down and plucked some fungus from the grass. ‘Field mushrooms’ he said ‘try these for breakfast’.
I drove round the field for a camping site. There was much sloping ground but I settled for the top end ..where the ground was level and sheltered by woodland.
From here, the advantage of the place became extremely clear. Huge views all around with only Dolbury hillfort occupying the higher ground along the spur to the north west.
Stuart visited us on the third day because of his interest in Devon Roman forts. He told us about his experience of finding a vicus (settlement) outside the fort at Okehampton near Dartmoor to the west.
This was one of a chain of forts, constructed in the 40s AD, marking the route of the Roman army as it captured territory from the peoples of what are now Devon, Somerset and Dorset… pacifying the wild west…. with the fortress of the II Legion Augusta established at Exeter.
We wondered whether other lines shown on the Killerton 1984 photo might relate to an Iron Age settlement pre-dating the fort. Alternatively, the lines may be the remains of structures constructed by people attracted to the fort in order to trade with.. and offer services to the soldiers.
I mentioned that fieldwalking had produced nothing here which could be dated to the Roman period. His reply was reassuring. Okehampton was much the same, despite careful excavation only a few scraps of 1st century Roman pottery were found in the beam slots and ditches of the settlement.
Another thing that bothered us was the lack of entrances. There was a good shape to our triple-ditched enclosure but no clear gaps. Gates should be found in the centre of at least two or usually all four sides of a Roman fort.
We worked hard and the HART team are now good surveyors and will go back and do some more of the field in the near future. Geophysics is like fishing.. you are never sure of the results until you land the catch… or the readings are downloaded and seen on the computer screen.
The magnetometry had been seriously affected by the huge steel gas pipeline and to a lesser extent by a water pipe. The sky-high ferrous readings bleached out the subtle responses from the archaeology. However, following ‘despiking’ and using various other processes on the Geoplot programme, the fort defences gradually emerged …and there, on the south side, near the centre was a clear entrance though the three ditches.
Parts of the enclosure circuit were visible on both types of geophysical survey plot and this now confirms Killerton’s Roman fort. The 1984 image wasn’t the result of some curiously appropriate plough pattern but in fact (which was more likely) demonstrated real archaeological features cut into the bedrock almost 2000 years ago.
Where I camped….. on the north end of the fort, the ditches were shown to continue under the woodland into the neighbouring field.
I fried and ate the mushrooms there…early one morning, watching the sun rise out of the Blackdown Hills, listening to the bells ring from the cupola on the Killerton House stable block…. and Derek was right… they were the best I have ever tasted.