Llancaiach Fawr is a tiny valley in South East Wales named for the Nant Caiach, a stream that runs through it. The location has been inhabited for about 4,000 years. They suspected that a previous home existed on the site, either beneath the current house or incorporated into the eastern end of the structure.

Llancaiach Fawr Manor was originally assumed to precede the Acts of Union between Wales and England of 1536, as they were referenced in John Leland’s Itinerary of 1537. The Time Team’s tree ring dating estimates a felling date for the roof timbers (those with enough sapwood left to test) of between 1548 and 1565, which is later than previously considered. Leland’s Itinerary could thus be referring to an earlier house on the site or a house belonging to the Prichards in the parish of Gelligaer—the parish formerly included Dowlais near Merthyr Tydfil, which is where this branch of the family originated, so Leland could be referring to their house in Dowlais.

The hunt for the house’s beginnings continues, and the presence of mediaeval ridge and furrow plough markings indicates that the ground surrounding the current manor has been used for agriculture for a long time. Carbon dating has dated the construction of a massive palisaded enclosure in the neighbouring field to 1494 BCE; the optimal characteristics of trackways, water, and level ground have made this little region a desirable place to live for millennia.

The Prichard (ap Richard) family erected the Manor House when “gentle birth” was no guarantee of security and it was meant to be guarded. The walls are 4′ (1.2 metres) thick, and the only way to get from one floor to the next was to use steps built into the walls. If the house was attacked, it could be split in half, and only those in the protected east wing had access to the latrine (toilet) tower. The turmoil of 16th century Glamorgan is further evidenced by the sturdy floorboards and modest ground floor windows.

With time, the Prichard family began to make changes to their home to demonstrate their expanding wealth and prosperity. The Grand Staircase was erected in 1628, and two rooms were elegantly panelled and other intramural stairs. A formal garden was also created during the same period.
Because of the corridors and stairways that have been sealed up over the years, there are more windows visible from the exterior of Llancaiach Fawr Manor than there are on the inside.