Brecon Castle was begun in 1093 by Bernard de Newmarch, when (as my book ‘Welsh Castles’ puts it) ‘he established his lordship of Brecon.’ The Normans had only come to Britain in 1066 and it was a wild time on the borders between England and Wales as they tried to gain control over the Welsh lands. The Chronicle of the Princes (Red Book of Hergest version) says (for 1093) “the French devastated Gower, Cydweli, and the Vale of Tywi; and the countries remained a desert.”
The lands had been occupied since before the Romans came, as Pen-y-crug hillfort, or Caer Coch, sits to the northwest of the castle. http://www.wisdomofrhiannon.co.uk/Brecon.html
Brecon Castle was much fought over. From Newmarch, the castle passed to the Braose dynasty. King John seized it from William de Braose, who was in rebellion, in 1207 and William’s son Reginald recaptured it during the Magna Carta war. In 1241, it passed to the Earls of Hereford, the Bohuns. (Welsh Castles, Adam Pettifer, p. 8).
During the Barons war of 1263-65, both Llywelyn ap Gruffydd and the Bohuns allied themselves with Simon de Montfort. Humphrey de Bohun ruled Brecon at the time. He had been the guardian of Gilbert de Clare, but when Clare switched back to King Henry’s side, Clare took it upon himself to capture Brecon Castle from his former guardian in 1264. In 1265, Llywelyn ap Gruffydd took it from Clare (but note, didn’t give it back to Bohun). By then, things had begun to fall apart for Montfort. Soon he was dead, along with the Earl of Hereford’s son, Humphrey. (Llywelyn ap Gruffydd, J. Beverely Smith, 1990)
Llywelyn lost control of those lands with the treaty of 1277, although he was much besieged through the 1270s. (ibid p. 358)
Of the castle itself, it is set between the Honddu and Usk Rivers. “There were two entrances as well as the postern gate. The main gate faced west and overlooked the Usk. It was approached across a drawbridge and probably guarded by two semi-circular towers and the usual great door and portcullis. From the town direction the castle was also guarded by a drawbridge on the site of the present bridge which crosses the Honddu. These gates were joined by the encircling curtain wail. which enclosed the whole area of the castle. Within these outer defences the most imposing building was the great Hall; this was the social centre of the castle and the Lordship where the Lords of Brecon held court when in the area. (The surviving medieval halls at Christ College – across the river from the castle – give a good idea of what it must have looked like inside. The private apartments of the Lord were next to the Hall. There are references to other rooms and buildings in the medieval documents. For example the Constable and the Receiver (of taxes and dues) had their own chambers. There was a chapel, exchequer, kitchen, harness tower, stable and porter’s chamber. The well was described as being 30 feet deep. These buildings suggest that the castle was more like a bustling town than the romantic, military fortress of imagination. People from the surrounding Lordship came to the courts held at the castle, they paid their dues to the exchequer, they pleaded for privileges or came with supplies of food, timber and other necessaries.” http://www.castlewales.com/brecon.html
The castle is mostly destroyed now and parts of it have been turned into a hotel. The only plan is above, from Speed, 1610: http://www.breconcastle.co.uk/brecon-castle-history.asp
Brecon Castle plays an important role in my After Cilmeri series.