Tunnel Tigers is a colourful portrait of the off-beat characters who worked on Scottish hydro projects, and of the tensions that were created when men of various religious and ethnic groups shared the same space.

Tunnel tigers are an elite group of construction workers who specialise in a highly paid but dangerous profession: driving tunnels through mountains or underneath rivers or other large bodies of water, in locations as far apart as Sydney and San Francisco. At the turn of the last century they tunnelled out the subways under New York and London; in the 1940s and 1950s they were involved in a score of huge hydroelectric tunnels in Pitlochry and the Highlands of Scotland. They continue with their dangerous craft today in various locations all over the world.

Many of these daring men were born in north west Donegal, Ireland, where the tunnel tigers were viewed as local folk heroes because they had the bravado to work in dangerous conditions that few other working men could endure.