Llancaiach Fawr Manor is a Tudor manor house near the village of Nelson, located just to the north of the site of the former Llancaiach Colliery in the heart of the Rhymney Valley in South Wales. The semi-fortified house was built on the site of an earlier medieval structure, either on top of the previous dwelling or possibly incorporated within the eastern end of that building. It is a Grade I listed building and is now best known as the home of Colonel Edward Prichard (died 1655), who hosted a visit by King Charles I of England in 1645.
Llancaiach Fawr Manor was at one time thought to have predated the Acts of Union between Wales and England of 1536 and was talked about in John Leland’s Itinerary of 1537. The manor house is thought to have been built in about 1530 for one Dafydd ap Richard. (Prichard being a modernised form of the patronymic "ap Richard"). However, dendrochronology results (from a Time Team excavation) indicate a felling date for the roof timbers of 1548–1565, later than was originally thought.
The Manor is considered to be one of the most important gentry houses to have survived from the 16th and 17th century period. It is now open to visitors as a living history museum.
When Civil War broke out between King and Parliament in 1642, Colonel Edward Prichard of Llancaiach Fawr was appointed Commissioner of Array to the King, raising men and money for the Royalist cause in Glamorganshire. His wife, Mary, was the sister of Bussy Mansell, a zealous Parliamentarian.
By the middle of 1645 support was waning and King Charles toured South Wales in an effort to rally support. He visited Llancaiach Fawr on 5 August of that year. (A silver coin with Charles's image, dated 1645, is among artefacts found by archaeologists in the grounds of the house.) Shortly afterwards, the Prichards and many other Glamorgan gentry changed sides to support Parliament. Later in the year, Colonel Prichard was appointed Governor of Cardiff Castle. In February 1646 he staunchly held the Castle for the Parliamentarians against a siege headed by Edward Carne. He was also commended “for his constancy in that affray” after the battle of St Fagans (1648), by Colonel Horton, the Parliamentary victor.