As Joe Marler alluded to while announcing his retirement last week, international rugby can be something of a "dream bubble".

But towards the end of last month, as the Ireland squad gathered in Portugal and began to look towards Friday's mouthwatering rematch with the All Blacks, they were served a powerful dose of reality.

The Irish squad have had several guests in recent years, from Bono to Shane Lowry. Hearing from personalities outside of the Test rugby grind can be illuminating and light-hearted, a welcome break from training and meetings.

But perhaps no visit stirred their souls quite like Nando Parrado's.

Parrado was once a rugby player, but he is more widely known as a central figure in a story at once inspirational and harrowing, one that exemplifies the strength of human spirit in the face of the greatest adversity.

In October 1972, a plane carrying members and family from Uruguayan club Old Christians Club crashed in the Andes on its way to Chile.

It was a horrible tragedy. Twenty-nine of the 45 people onboard - including Parrado's mother and sister - lost their lives. Those who survived were forced to eat those who had been killed in the crash.