An Online Community Newsletter published by the Pencoed Town Council
There is evidence around South Wales, but not in Pencoed itself, that the first men walked the area in a warm inter-glacial period between 35 and 25 thousand years ago. The area would then have been the home to mammoth, woolly rhino, wolves, reindeer and wild horse. The countryside would have been covered with huge forests of oak, birch and hazel.
Around 4,000 to 2,000 BC, the climate became wetter and cooler, and earlier Neolithic settlers would possibly have been clearing the forest for agricultural use. There is ample evidence in and around Pencoed of these early settlers in the form of settlements and burials. There were finds, in 1884, of flint implements and animal bones in a cave at Coed-y-Mystwr.

About 500 BC, with the ingress of further immigrants and the area appears to have been unstable and violent, as can be evidence by the construction of hill forts at St Mary Hill (to the south of the town) and on Mynydd-y-Gaer (to the north). These peoples were of course the Celts, who had migrated over hundreds of years from central Europe.
The next visitors were the Romans in the first century AD. There have been ample finds of Roman artefacts in the surrounding area, particularly around Cowbridge (five miles south of Pencoed), but nothing around Pencoed itself. What is now the A48 road was at that time a major Roman road, which ran between Cardiff and Carmarthen. This remained the main route through South Wales (skirting Pencoed) for nearly 2,000 years until the building of the M4 Motorway through the town.
After the Romans departed in the 4th Century, the local inhabitants, the Celts, successfully defended the land from invasions by Vikings, Angles and Saxons. There is evidence that part of the nearby church at Llanilid (a mile to the east of Pencoed) dates from this period. However, in the 11th and 12th century, the Normans appeared on the scene and things changed dramatically.