A major event associated with Delgany occurred in AD1021 or 1022, and took the form of a battle fought here between Ugain , King of Leinster, and Sitric, the Danish king of Dublin, during which the latter was defeated .
This battle was recorded in the Annals of Ulster, and in the Annals of the Four Masters as “a great slaughter on Sitric, son of Aulaf, and the Danes of Dublin by Ugaire, son of Dunlang, King of Leinster, at Dergna Mo Goroc (S. Mogoroci) in Ui Bríuin Cualan” . Apparently Sitric was on his way to attack Glendalough for the second time in four years when he was engaged at Delgany and the event has prompted speculation that Sitric had a stronghold in the area .
Another account records the event as “a slaughter of the foreigners in Uí Briúin Chualann”.
The territory of Uí Briúin Chualann extended from what is now south County Dublin into the Wicklow coastal lowlands as far as Newcastle , and the latter account may suggest that Viking settlers were dispersed throughout the region. Indeed, Price suggests that the region was “an area of Scandinavian settlement” . Interestingly, nearby placenames Windgate and Collagad may contain the Old Norse term gata, meaning ‘path’ or ‘road’, and it has been suggested that this could refer to an ancient route linking Bray and Delgany, and perhaps extending even to Arklow .
At that time “Delgany could be reached from Bray by an old Norse road
which ran through the centre of the townland of Coolegad leading from Windgates past Templecarrig House to Kindlestown Castle and on to the village itself” .
Although the exact site of the Battle of Delgany is unknown, there are local stories about ghosts being seen on the road from Delgany to Blacklion. Flannery suggests that the engagement may have taken place on “the low hillflanked valley of the Three Trout stream along the present Glen Road” .
No other major historical events appear to have been recorded in Delgany in the Middle Ages. Towards the end of the twelfth century, the area was apparently part of the patrimony of the Mac Giollamacholmog clan, along with Kellegar, Ballyman, Kilmaberne and Ballydonagh (Simpson 1994:193–94, cited in Courtney Deery 2016). This
clan allied themselves with the Anglo-Norman invaders who took Dublin in 1171.
5 Flannery notes that Ballydonagh or Baile Ui Dhunchadha, part of which would later become Bellevue Demesne, had been the territory of the O’Donchadhas “who were the principal clan in the area in pre-Norman days” (Flannery 1990:45). In 1241, the
lands of Delgany in the Barony of Rathdown were held by Henry Prudum or Prodholme from the Archbishop of Dublin. Forty years later, the “Eccesia de Delgeney” (the church of Delgany) was under the charge of Dominus Johannes Patrick, under the patronage of the Archbishop of Dublin (Flannery 1990:16).