Like all of the first Norman castles in Britain, Abergavenny was originally a motte and bailey structure. However, it was modernised and developed into a formidable structure in the early 12th century. By 1170 the castle comprised a stone keep, an imposing gatehouse and a great hall, all surrounded by a large curtain wall.

Abergavenny Castle had been built by the Norman Lord Hameline de Balun in approximately 1087, soon after the Normans made their first incursions into Wales. Sitting above the River Usk and the Usk Valley, the castle was intended to defend against Welsh attacks from the north into the fertile plains of what is now the county of Gwent.

Christmas is normally a time of goodwill and friendship to all mankind but in the 12th century such gestures and emotions were very far from people's minds. This was particularly the case in the now ruined Norman castle at Abergavenny, the scene of one of the most infamous massacres ever to take place in Wales.

Despite what might seem formidable defences, in 1172 - soon after it had been developed and extended - the castle was actually besieged and captured by Sytsylt ap Dyferwald, the most significant Welsh chieftain in the area. Welsh occupation did not last long, however, and the castle was soon returned to the de Balun family.

It was a wild and dangerous time to live on the borders of England and Wales. Fighting between the incomers and the native Welsh was constant and sometime in the 1160s Henry Fitzmiles, son of de Balun, Lord of Abergavenny, was killed fighting against the forces of Sytsylt ap Dyferwald.

With Henry dead there was no male heir to take over the de Balun lands and these consequently passed to William de Braose, the husband of one of the daughters of the Norman lord. The powerful and imposing Abergavenny Castle was now in the hands of a man who was to prove one of the most reckless and vicious of all the Norman Barons.

At Christmas 1175 de Braose invited Sytsylt, his son Geoffrey and all of the leading chieftains from Powys to a feast at Abergavenny Castle. The intention, he declared, was to meet and spend the Christmas period in each other's company. They would feast and celebrate and make a lasting reconciliation following the death of Henry Fitzmiles.

Unsuspecting, Sytsylt accepted the invitation, happy to bring peace to the land, but William de Braose had other intentions. Reconciliation was the last thing on his mind.

With weapons stacked outside and the ale flowing, the doors to the great hall were suddenly locked and a massacre began.

Sytsylt and all his allies, his son and his followers, were callously cut down in an act of vengeance for the death of Henry – although quite what de Braose was thinking is difficult to analyse. After all, Henry's death had brought him ownership of vast swathes of Welsh countryside. He should have been grateful to the Welsh.

The massacre was bloody and brutal, dozens of unarmed Welsh chieftains being cut down by the soldiers of William de Braose. William Camden, the great writer and antiquary of the 16th century, was moved to write that Abergavenny Castle "has been oftener stained with the infamy of treachery than any other castle in Wales."

In a time and a land where killing and slaughter were fairly commonplace, that is a comment of some significance and note.

The massacre did not sit well with the English monarchy. Further trouble on the borders was the last thing that was needed. William was effectively removed from control of his lands and the castle at Abergavenny passed to his son, also called William. It did not stop the ill will and bad feeling between Normans and Welsh – and it did not stop warfare, either.

The Welsh had their revenge when, in 1182, Abergavenny Castle was attacked by Hywel ap Iorwerth. The castle was taken, the governor and his wife captured – and then the castle was burned.

A time of peace and goodwill? Clearly not in 12th century Wales.