It is widely accepted that Neolithic people first laid out many ancient sites in areas such as the Vale of Glamorgan. With the demise of the Neolithic civilisation these sites were taken over by their successors and frequently were used for religious or other public purposes. This process continued down the centuries with a new civilisation seeking to suppress the ways and religions of the old, culminating in the last thousand years with Christian churches being built on many sites.

Ancient sites had no doubt many purposes. Some would have been religious, others for burial, and others again for the care of the sick or for public meetings; still others, in suitable locations, were fortified, either then or later. Roads and trackways connecting these sites – there seems at least some evidence that these people liked straight lines – continued in use and were built up by others, principally the Romans, who also liked straight roads.

So today ancient sites may well lie under all manner of edifices. Hospitals, castles, churches, Roman roads, fortified sites from the Iron Age, may all indicate an ancient site. But it is also necessary to remember that many such modern constructions were built on virgin sites as well and others were moved a short distance for one reason or another – perhaps to accommodate a road, or to avoid a difficult piece of ground – from their original locations.

For this reason it is hard to be sure that a church, castle or hospital really does cover an ancient site that had been built over unless there is some good confirmatory evidence. With so many potential candidates for ancient sites it is all too easy to discover straight lines or circles on a map. By itself this cannot confirm that a site is ‘ancient.’ Something more is required and that is to be able to demonstrate that the site is located with reference to other sites or geographical features, using lines that can be measured in whole number distances, or which are bisected in whole number ratios.