On Christmas Day in 1175, William de Braose, a Marcher lord (the 4th Lord of Bramber), summoned Seisyll ap Dyfnwal, Seisyll’s eldest son, Geoffrey, and a number of other local leading Welshmen from Gwent to Abergavenny Castle to hear a royal proclamation.   He then murdered them all.  This was justified in William’s mind because of a prior killing of his uncle by Seisyll (or so he suspected, though apparently had no proof).  “De Braose and his men then mounted horses and galloped the few miles to Seisyll’s home where they caught and murdered his younger son, Cadwalladr a boy of seven years of age and captured his wife, whose exact fate is uncertain.” http://en.wikipedia.org/wiki/Seisill_ap_Dyfnwal

Other sons, not in attendance that day, got their revenge by burning Abergavenny in 1182.  Gerald of Wales “alludes to the horrible event in the history of Abergavenny Castle described above, during his famous journey through Wales of 1188, but refuses to mention the incident specifically, saying least (the story) serves to encourage other equally infamous men.”

William Camden, the 16th-century antiquary, said that Abergavenny Castle “has been oftner stain’d with the infamy of treachery, than any other castle in Wales.”  http://www.castlewales.com/abergav.html

And that’s saying a lot.

“From its early beginnings this was an important castle, the headquarters of the Norman lordship of Abergavenny, used for accommodation by kings if they were in the locality. It stands on a spur above the river Usk, in a good position to secure the valley and prevent Welsh incursions into the lowlands.”  http://www.castlewales.com/abergav.html

“The Motte was probably built by the Norman Lord Hamelin de Ballon in 1087 AD. The tower built at the top of the motte would have been wooden. Beneath the motte was the bailey – a courtyard containing the outbuildings and stables.”  http://www.abergavennymuseum.co.uk/index.php?lang=EN;navId=3

Jeff Thomas writes further:  “Practically all the Marcher Lords were forced to deal with a rebellious and resentful Welsh population in violent ways in order to protect their newly-awarded “kingdoms,” but de Braose time and time again seems to have gone out of his way to commit acts of cruelty that went beyond his contemporaries. Although some would say his family eventually got what they deserved, the extinction of the male line and a forfeiture of all lands, de Braose stands out as an example of what the native Welsh population were up against, and why they rebelled so ferociously against the Norman invaders.”

Gerald of Wales “also mentions Abergavenny in a later passage following it’s recapture from the Welsh by English forces. As the Welsh were besieging the castle ‘two (Norman) men-at-arms were rushing across a bridge to take refuge in the tower which had been built on a great mound of earth. The Welsh shot at them from behind, and with the arrows which sped from their bows they actually penetrated the oak doorway of the tower, which was almost as think as a man’s palm. As a permanent reminder of the strength of their impact, the arrows have been left sticking in the door just where their iron heads struck.’ Gerald notes that the men of Gwent ‘are more skilled with the bow and arrow than those who come from other parts of Wales.'”  http://www.castlewales.com/abergav.html

*Thanks to Stephen Colbert’s Better Know a District