There is a series of shallow depressions in the eastern part of the heath. One or two are circular, the rest are irregular in shape, and all are about 1 to 1.5 metres deep. Were they once clay pits?
There are several pieces of evidence that point in this direction. First, they do not appear natural — especially the circular ones. The fact that there is no bank around them suggests that the material dug from them has either been spread thinly round about or been taken away. If it had been spread thinly, that still leaves the question of why were they dug.
Second, the heath sits on an outcrop of Oxford clay – oval in shape and about 0.5 km wide by 1.8 km long – that lies on the high ground to the east of the Banbury Road and runs from around the trig point across the heath and through Tackley Wood (see this British Geological Survey map). The clay is just below the topsoil. There are also several ponds on the clay: just east of Old Man Leys Farm; in the north-eastern corner of the heath; and in Tackley Wood. Others that have silted up or been filled in can be seen on the original 25-inch and 6-inch Ordnance Survey maps which date from the late 19th and early 20th centuries (these are available – digitised, searchable and free – on the National Library of Scotland website. The ponds lie on high ground, and it is difficult to see how they could have been formed naturally. So they too could also have originally been clay pits.
Third, the trig point is in the field called Tacknalls; and about 200 metres down from the trig point towards the village is the site of a brick kiln which is marked on the Gardiner estate map of 1787. No trace of the kiln remains above ground. The site of the kiln is close to two further depressions which are right on the edge of the clay outcrop and which must have been the source of the clay for making bricks.
Putting these together there is a plausible case for the depressions on the heath being clay pits. If so, what was the clay used for? The brick kiln in Tacknalls was probably in use not long before it was marked on the map, say around 1770. It was most likely associated with building works on the estate by the last John Morton who died in 1780 and who was responsible for enlarging and remodelling Hill Court.
Or the bricks may have been used in working buildings on the estate. It was not uncommon in the late 17th and 18th centuries for ‘improving’ landowners to set up brickworks on their estates. Is there any surviving physical evidence for the use of bricks in the village in the 18th century? Most of Hill Court was demolished in 1959, so we don’t know if brick was used in its remodelling. If there were clay pits on the heath, they may also have been used for brickmaking in the 18th century, but any evidence on the ground is invisible under the bracken.
Stone has been the main building material here for centuries; and before that wood, turf, wattle and daub. But much earlier we had a Roman villa at Street Farm – built of stone and wood, not brick – but roofed partly with classic Roman ceramic tiles. Were they made here with our local clay, or were they brought in? Was there small-scale production of Roman tiles here? The Street Farm villa alone might not have generated enough demand.
But there is the possibility of another substantial Roman building, even a villa, in Nethercote; and broken pieces of Roman tile occasionally turn up among the pottery scatters around the village, suggesting that the Roman farmsteads here may also have been partially tiled. Chemical analysis of tiles from the villa might settle the question.
Tackley clay turns out to be excellent for making pots. The Local History Group has organised two pottery days in which local potter Jane Bowen helped many of us build coil pots using clay dug from Tim and Pam Laughton’s land. The children’s pots were fired in Jane’s electric kiln while the adults’ pots were wood-fired experimentally in the open in a pit next to where the clay was dug. The latter turned out black because they were fired under a clump of turf which kept the oxygen out and created a reducing atmosphere, whereas the children’s pots were bright orange from being fired in an oxidising atmosphere. Some of the pots didn’t survive being fired outside, but some did, indicating that Tackley clay could certainly have been used locally for pottery. But was it?
There is much Roman pottery scattered on Tackley’s fields, evidence for the presence of the villa and a number of farmsteads. It is made up of both oxidised and reduced wares and is wheel-thrown. But it wasn’t made around here. Rather, it was imported from known and identifiable pottery-producing sites across the southern part of the Roman province, and even from across the Channel in southern France.
But we do have much smaller quantities of pre-Roman pottery from Bronze Age and Iron Age sites around the village, dating back to 1500 BC. Much of this is fairly crude and would have been made locally, when a household needed it, rather than being traded over a distance.
If there were clay pits on the heath, was that where Tackley’s Bronze and Iron Age farmers got the clay to make their pots? Or are there too many pits to be explained by such a small and irregular demand?
Tackley’s is the last readily accessible deposit of high-quality clay as you go westwards and northwards into the Cotswolds. Could the clay on the heath have been a valuable resource more widely?
Finally, perhaps the clay was used raw as a building material itself, either as wattle and daub – a mixture of wet soil, clay, sand, dung and straw – or mixed with soil and straw as cob, or as a flooring. None of these uses would leave archaeological traces.
Research and text: John Perkins