The man who invited the Normans
Diarmait
Diarmait Mac Murchada was King of Leinster from 1127. By 1166 he had been driven out by a coalition under Ruaidrí Ua Conchobair, the High King - there was a stolen wife somewhere in the back of it, the Abbess of Kildare, his neighbour Tighearnán Ua Ruairc nursing the grudge for fifteen years. Diarmait sailed for Bristol, found Henry II in Aquitaine, got a letter of permission, and recruited Richard de Clare - Strongbow - with the offer of his daughter Aoife in marriage and the kingdom after his death. The Normans landed in Wexford in May 1169. By 1171 Diarmait was dead and buried in the cathedral graveyard at Ferns and Strongbow was Lord of Leinster. The high cross shaft in the graveyard is reputed to mark his grave. The story Irish schoolchildren learn - that he sold the country - is the simple version. The slightly less simple version is that he played a regional power game and the table tilted.
The founder, also called Mogue or Maedóc
St Aidan of Ferns
The monastery at Ferns was founded around AD 598 by St Aidan - known locally as Mogue, or Maedóc, or in scholarship Máedóc of Ferns. He was a Cavan man, born on an island in Templeport Lake, trained at St David's in Wales, and granted the land at Ferns by King Brandubh of the Uí Cheinnselaig after a battlefield favour. He became the first Bishop of Ferns. The diocese named after him is still a Catholic see today.
The greatest knight
William Marshal
William Marshal married Isabel de Clare, Strongbow's daughter, in 1189 and inherited Leinster through her. He built the stone castle at Ferns around 1220 to plant a Norman fist on Diarmait's old capital. Square keep, four round corner towers, vaulted chapel built into one of them. Marshal himself was probably the most celebrated knight in medieval Europe - tournament champion, regent of England for the boy-king Henry III, the man who held the realm together after Magna Carta. He is not buried here. But the castle is his.
When the Irish came back
The Kavanaghs and 1346
The Marshalls and their successors held Ferns Castle until 1346, when the Irish clans - the Kavanaghs descended from Diarmait's own line - burnt it and took it back. They held the town and the castle for the next two centuries until the Tudor reconquest under Henry VIII reabsorbed it in 1540. The castle never recovered its full form. What you see today is essentially what the wars of the 1640s left standing - half a keep, one good tower, and a chapel that survived everything.