Castell Caergwrle is located on the English/Welsh border in Flintshire. The castle was built by Dafydd ap Gruffydd on land given to him by King Edward after the war of 1277 as a reward for serving him and betraying his brother, Llywelyn.
Caergwrle was built on an ancient site that had been occupied since before Roman times. The first reference to the medieval castle states that Edward had sent 100 marks to Daffyd on 12 November 1278 to either start building or repair a castle that is already there. Then, in 1282, after Dafydd rebelled against Edward and started the war anew, the king sent Reginald de Grey to take the castle. But when forces arrived on 16 June, they discovered Dafydd had already retreated and abandoned the location, to the point of filling in the well. Grey immediately set about refurbishing the castle, even to the point of enlisting James of Saint George, the great castle designer of Harlech, Caernarfon, and Conwy. According to the records, more than 340 carpenters, over 600 diggers, and up to 35 stone masons worked on the site.
Notable features included two D-shaped towers and a circular keep that overlooks the approach to the south-east. Not surprisingly given its initial owner, Dafydd, the castle incorporates English elements in what is basically Welsh pattern. A single curtain wall survives on the east and is fronted by a ditch. Openings for latrines at first floor level can been seen in the curtain wall along with two large holes in the west wall one of the towers that would have contained timber beams supporting the canopy of an internal fireplace.The castle burned in a fire a year later, in August of 1283, and was never rebuilt.
The post-Roman hill fort is a setting in The Last Pendragon Saga.