Mario Sepulveda is weeping. Amid the clatter and din of the building site on which he is working, in the Chilean capital, Santiago, Mr Sepulveda’s voice can hardly be heard as it comes in great heaving sobs.

Saturday was his 44th birthday – and the day his mother died, while giving birth. He’s never seen a photograph of her; the pain, he said, remains incredibly raw.

And Saturday was also the day he travelled 500 miles north of his home to the dusty mining town of Copiapo – the place where, four years ago, he became trapped in an underground mine, leading to one of the most miraculous rescue efforts of our era.

“It’s quite an emotional time for me,” said Mr Sepulveda, apologising to The Telegraph for his choked voice. “The past four years have been intense.”

The story of how Mr Sepulveda and 32 colleagues – universally known as “Los 33” – survived for 69 days underground, before being hauled one-by-one to the surface in an unprecedented triumph of engineering, captured the imagination of the world.

Their tale is being told in a Hollywood film, with Antonio Banderas starring as Mr Sepulveda and Juliette Binoche as the sister of another miner, Dario Segovia. Filming is completed, with the premiere due at the end of this year.

And this week sees the long-awaited publication of their book, Deep Down Dark, which tells the story of the men and their ordeal half a mile beneath the desert.

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