The second and concluding programme, Diarmuid Gavin (the gardener) picks up the trail of the first Irish at La Mer de Glace, one of Europe's largest glaciers, near Chamonix, France. Today the slopes are packed with skiers but, 20,000 years ago, it was a different story.  As the ice tightened its grip, most of the continent of Europe - but not Ireland - had been penetrated by small groups of nomadic people. They had ventured north on an epic journey out of Africa that had taken millennia. But the ice forced people south and places like Northern Spain became a vital refuge for our species. How things have changed. Then, around 12,000 years ago people ventured north again and, as we now know, the ancestors of the Irish were among them. But how did they make it to our island.