Tar at Tara: Ireland's most expensive motorway is also its most controversial. The new M3 links Dublin with Meath and Cavan but also runs through the Tara Skreen valley; a place of mythological legend.

The Irish government says the road is a vital piece of infrastructure, but conservationists and archaeologists are furious at what they say is a desecration of Ireland's richest area of archaeolgical heritage.

Diarmaid Fleming tells the story of the conflict between the old and new Ireland. Show less