A 64-year-old farmer has been fined €25,000 at the Circuit Criminal Court in Tralee for destroying a 1,000-year-old ringfort, which was a protected national monument.

In one of the first prosecutions of its kind to come before the courts, John O'Mahony pleaded guilty to carrying out work on the fort on his farm at Causeway in Co Kerry in February 2008, without notifying the National Monuments Service in advance.

Mr O'Mahony farms around 40 acres at Clashmealcon near Causeway in north Kerry.

A ringfort and series of souterrains or underground tunnels - which are thought to have been constructed over 1,000 years ago - were on the lands, and these are protected national monuments of historical significance.

Mr O'Mahony hired workers to demolish the majority of the ringfort and the the court was told that the material was used to fill in a pond which Mr O'Mahony believed was dangerous.

The court heard that Mr O'Mahony had not sought permission from the National Monuments Service of the Department of Arts, Heritage & the Gaeltacht and restoration of the fort was not possible.

Mr O'Mahony knew of the existence of the ringfort, because he had previously objected to a planning application there on the grounds that the land contained "an historical ringfort".

He had only bought the lands two months before work on the ringfort was carried out.

His barrister, John O'Sullivan, said Mr O'Mahony apologised. He said his client did not know he had to seek permission for the work and did not understand the implications.

Judge Carroll Moran said ownership of property is a right, but this right was not "unfettered" and was qualified by the fact that property was held in trust for the culture of the country.

At a previous hearing he warned that "a marker" would have to be put down when it came to imposing sentence.

The maximum penalty which Mr O'Mahony faced was five years in prison and/or a fine of €50,000.

