The discoveries have been made at the 1250-built St Mary’s Collegiate Church in Youghal — the longest, constantly used church in the country.

Archaeologist Caroline Desmond said they moved onto the site after subsidence was noticed in the aisle. Discoveries show that in the 17th century, Youghal was a far more prosperous town than Cork and had more trade in its port.

Excavations began six weeks ago and they discovered vaults underneath the aisle.

One vault, dated February 1661, contains the remains of John Luther, an alderman of the town and his wife, Elizabeth.

Another vault, dated 1678, contains the remains of one of the Earls of Desmond, John Fitzpatrick.

The other vault has yet to be dated and archaeologists don’t as yet know who is interred in it.

“We have unearthed some pottery and coins from the 17th century and a fabulous underground central heating system which was modelled on Roman aqua duct system. It dates to the 18th century and boiling water was poured in to provide the heating,” Ms Desmond said.

She said the main job now was to stabilise that section of aisle and cover over the artifacts.

The project has been funded by the Department of Arts, Culture, and the Gaeltacht along with Cork County Council.

“We will have to come back again next year to do the remainder of the aisle. We will have to reapply for funding to do this and I have to say, the Department of Arts, Culture, and the Gaeltacht and the county council have been very good to us.”

Ms Desmond said annals showed there were eight tombs under the aisle, so five remain to be uncovered.

“We will undoubtedly find more archaeology there. The roof of the church is still the original and it was built by French carpenters. That also goes to show that Youghal was a very prosperous town at the time as the merchants were able to pay to bring in skilled labour from abroad,” she said.

Richard Boyle, the first Earl of Desmond, is also buried in the church. He moved to Youghal after buying a lot of land in the area from Walter Raleigh.