The Castle was supported by the small town of Cefnllys built at the base of the hill, but when the castle itself became a ruin, the town gradually disappeared and now only the 13th century church remains. The remains of the castle are at the top of 'Castle Bank'.
First built by Roger Mortimer, it was also known as Castell Glan Ithon (after the picturesque river) and it played its part in the border fighting between the Welsh and English. It was destroyed during the fighting of 1262.
A more substantial castle was built at the south west tip of the hill around 1273 and it survived until the late 1400s when the manorial court was transferred to the Neuadd - pronounced 'Niath' - meaning Hall or Court. This is a 16th century building, now a Grade II listed farmhouse, near where the castle once stood. The Neuadd Farm currently offers excellent Bed and Breakfast accommodation and facilities.
King Edward III of England, married (1328) Philippa of Hainault. Their son, Edmund, Duke of York, married (1372) Isabella of Castile. Their son, .Richard, Earl of Cambridge, was married (c.1406) to Anne Mortimer.
Current Drew-Smythe family descends from (inter alia) Anne Mortimer.
Anne Mortimer was the daughter of Roger Mortimer who was b. 1373 and d. 1398 in a skirmish with the Irish at Kenlis and is buried at Wigmore, Herefordshhire. Roger Mortimer was the Earl of Ulster and 4th Earl of March. His father was Edmund Mortimer, 3rd. Earl of March and thus back to the original Roger Mortimer who built Castell Glan Ithon (Cefynllys).
The son of Anne Mortimer and Richard, Earl of Cambridge was Richard, Duke of York, who married (c.1438) Cecily Neville. Their son, King Edward IV of England, married (1464) Elizabeth Woodville. Their daughter, the Princess Elizabeth of York, married (1486) King Henry VII of England (the Welshman, Henry Tudor).