he Castleknock College Union is the society of pastmen of the college. It exists to help former students keep in touch with the college and with each other.
It was formed in 1896 and is as such the oldest such society in the country.
Among its activites are an annual dinner for pastmen, the graduation ball for those who left the college the previous year, regular golf outings and much much more.
The full website for the Union can be found here - Castleknock College Union