17 February 1980:The finding of the Derrynaflan hoard in Killeens bog Co. Tipperary in 1980 was one of the greatest archaeological discoveries of modern times.

Derrynaflan is a small island of mineral soil in Killeens bog Co. Tipperary. The site was an important monastery in the eighth and ninth centuries and came under the patronage of the King-Bishops of Cashel. The site is best known for the treasure discovered there in 1980, one of the greatest archaeological discoveries of modern times.

The hoard was discovered by Michael Webb and his son Michael Jr. while metal detecting at the National Monument on 17 February 1980. The hoard consisted of a highly decorated ninth century silver chalice, a large eighth century paten and stand an eighth century liturgical strainer and an eighth to ninth century bronze basin. The objects in the hoard date to different periods and did not originally constitute a single communion set. The treasure appears to have been buried in the ninth or tenth centuries to conceal it, probably from Viking raiders. The hoard is on display in the national Museum in Kildare St. Dublin.

The discovery of the hoard lead to years of legal action between the finders and the Irish state that went all the way to the Supreme Court. In the course of the legal action the law of Treasure Trove, which had operated in Ireland since medieval times, was found to be incompatible with Irish law. This resulted in the 1994 National Monuments Act that vested in the state the ownership of all archaeological objects.