Prince William's Seat[2] at 555 metres (1,821 ft), is the 296th–highest peak in Ireland on the Arderin scale,[3] however, it does not have the elevation to quality as a Vandeleur-Lynam.

[6][7] According to Irish academic Paul Tempan, the peak was probably named after William, brother of King George IV, following a royal visit to Ireland in 1821.

[2] Tempan has not been able to find any evidence of an Irish native name prior to "Prince William's Seat" (historical maps such as Wright's Guide to the County of Wicklow (1827), simply list the area as the "Commons of Ballynulty", a local townland).

[6] Prince William's Seat is described as a popular hill walking location for families given its ease of access and proximity to Dublin City.

[6][7] Near the summit of Knocknagon is a large granite Tor known as Fitzwilliam's Seat, which stands out amongst the flat boggy terrain of the area.