On Monday night I was at a poetry reading in Observatory. In the open mic section, after the featured poet had finished, an Irish friend of ours called Liam stood up and sang The First Time Ever I Saw Your Face in a lilting, beautiful voice.

It is a much-covered song, but most of these versions are irredeemably sentimental, drowned in strings real or synthesised. Ewan MacColl, the man who wrote the song for his lover Peggy Seeger and taught it to her over the telephone, had a special place in his record collection for these covers – apparently he called it his “chamber of horrors.”

It was, of course, made famous by Roberta Flack in a version that has its moments, but is ultimately weighed down somewhat by its string arrangement. However, there is a version by Johnny Cas hfrom his American IV: The Man Comes Around album that I find impossible to resist.

Cash’s late-career comeback saw him record definitive versions of several other unlikely songs – Neil Diamond’s Solitary Man and Sting’s I Hung My head come to mind - lending them an austere dignity that they never had before. But somehow it’s The First Time Ever I Saw Your Face that takes me by surprise every time.

Cash recorded The Man Comes Around shortly before his death, and this is likely to influence many listeners in its favour. But the stark beauty of his singing is disarming on its own terms, quite apart from any biographical details. Rather than disguise the technical limitations of Cash’s now much older voice, Rick Rubin’s sparse production emphasises it, and never to better effect than here.

It is an easy song to wreck – the evidence is unmistakable. MacColl himself apparently accused Elvis’ cover of it of sounding like Romeo singing up to Juliet from the bottom of the Post Office Tower, and I regret to report that this is a fair assessment.

The greatness of Cash’s version lies in the fact that it places his voice centre stage, so that one hears every word of it as if for the first time, which of course is exactly what the song demands in the first place: “The first time ever I saw your face / I thought the sun rose in your eyes / And the moon and the stars were the gifts you gave / To the dark and the endless sky …” By slowing the song down and keeping the accompaniment sparse, Cash manages to evoke the dark and the endlessness of that sky in the absence of the beloved.

After that you’d expect the song to go on without further surprises, but it is a shock when Cash’s ravaged voice says in the third and final verse: “And I knew our joy would fill the earth / And last till the end of time my love / The first time ever I saw your face …” Because what that voice evokes most strongly is transience, the possibility of a last as well as a first time. When a young pop singer like Flack makes such claims for love we smile and remember a time when we too felt idealistic about it. When a voice as beautifully fragile as Cash’s shortly before his death makes the same claim, it feels as if it has come from the ends of the earth to tell us something. We begin by being entranced by the apparent gap of time and experience between that voice and what it is singing about. And we end up surrendering to something so powerful that it makes us believe that time itself can disappear in the face of memory and the power of the human spirit.