Demonstrations at the Hill of Tara passed peacefully today as construction workers moved in to excavate the ancient site.

Campaigners blocked archaeologists and workmen from entering the newly discovered 2,000-year-old site at Lismullen early this morning.

But as gardaí and security staff arrived, protesters ended the stand-off.

Controversy has surrounded the site since the ruins were uncovered by workers constructing the M3 motorway last April.

The royal ceremonial enclosure, which lies across the northbound lane of the proposed M3 motorway, was declared a national monument by former environment minister, Dick Roche.

But in one of his final acts of office, he controversially signed an order of preservation by record for the site, meaning the prehistoric henge would be photographed, sketched and measured before being razed to make way for the motorway.