For rather a short book (259 pages of large print and generous spacing), Norman Thomas di Giovanni’s odd memoir of Jorge Luis Borges includes a surprisingly large number of pages devoted to urination. On page 57, the great Argentinian writer is caught short just before arriving back at his flat: ‘He let go with an almighty flow and splash of piss that echoed loudly in the empty stairwell … “That’s all right,” he said, “they’ll think it was some cat.”’ On page 149: ‘Urine was gushing in a heavy stream down his legs inside his trousers and squishing over the sides of his shoes. He made it to the urinal, but by this time his socks and shoes and tweed trousers were urine-soaked.’

On page 228, the accident happens on a plane: ‘I noticed … a plastic bag for air sickness. I grabbed it and held it open for Borges to use. When he finished there I was, sitting with a warm bag of piss in my hands.’ For good measure, di Giovanni also notes the ‘overpowering stench of feline urine’ left by the cats whose job was to assassinate the mice that ran riot in Borges’s place of work, the National Library in Buenos Aires. To invoke an old music hall maxim: ‘I do not wish to know that, kindly leave the stage.’

Borges, born in 1899, was quite an old man in the period covered by Georgie & Elsa – 1967 to 1970 – and it is well known that chaps of advanced years tend to suffer from unruly bladders. Most biographers of the elderly male prefer to gloss over this regrettable fact – Boswell is tactfully silent on the subject of Johnson’s micturation and biographies of, say, Churchill, Mandela, Gandhi, Newton, Tolstoy and other remarkable gentleman of ripe years have often been similarly discreet. Is this, perhaps, because the urgent need for a pee tells us nothing of their singular lives, save that they shared in our common human weakness? The only detail worth knowing about Borges’s frequent embarrassments is that he referred to a pee by the euphemism ‘an Old Norse’. Ever the Anglophile, Borges grew more and more interested in the family relationships between English and the ancient languages of the cold North.

The subtitle of di Giovanni’s book brags of an ‘untold story’. Well, some stories are untold because they have been suppressed and some because they are too lacking in significance to be worth telling. Unwary souls might buy this volume in the hope of shocking revelations – that Borges was, let’s say, actually a woman, or a CIA agent, or an alien from a distant constellation. In fact, the untold story pretty much boils down to this: late in life, Borges, known as ‘Georgie’ to his family, made the mistake of marrying a younger woman, Elsa Millán. Everyone agreed that she was utterly ghastly: uninterested in anything about Borges save his money, wildly spendthrift, philistine, loud, rude, bullying and light-fingered. The marriage made him very unhappy and three years later they divorced. As young people say: end of.

The translator of a good deal of Borges’s poetry and fiction, di Giovanni witnessed this sad period in Borges’s declining years. He clearly admired, and continues to admire, the grand old man’s writing, and refers to one set of poems as ‘moving … with a wonderful freshness and energy about them’. Less convincingly, he also stresses the closeness of the friendship that grew from their collaborations. Perhaps this was so, but the tone of di Giovanni’s reminiscences is hardly Boswellian in its warmth or respectfulness.

At various points, di Giovanni refers to Borges as ‘posturing’, ‘incredibly callow’, ‘ghoulish’, ‘sniffy’ and a ‘consummate gossiper’. He also depicts his subject as a snob, a racist (‘I don’t know what it was about black people, but he did have an aversion to them’) and a serial liar. The Borges of these pages is shown to be sexually impotent, selfish, occasionally ridiculous (he challenged radical student hecklers to duel with him) and, above all, weak and dithering. Borges’s mother, we learn, said of him, ‘The trouble is, Georgie no tiene carácter.’ Di Giovanni quibbles with Borges’s scholarship, too, recalling an occasion when they were discussing Macbeth: ‘Strangely, he misunderstood the words “making the green one red.” He once said to me, “Look, di Giovanni, Shakespeare has personified the sea.” Borges was reading it, “making the Green One red.”’ Indeed he was, and plenty of intelligent theatre directors have also chosen to favour that common interpretation.

Little of this spiteful matter makes for pleasant reading, so it is probably just as well that the book is padded here and there with documents from other hands: seven pages of briefing from a divorce lawyer, five from Borges’s list of marital woes and a large chunk from Foxe’s Book of Martyrs (by far the best prose in the book) about the executions of Latimer and Ridley, included to explain a single remark made by Borges during his divorce. This whiffs not only of roasting flesh but of desperation as well.

As is often the case with snide biographies, Georgie & Elsa inspires sympathy for the victim and sends one back to the thing about Borges that receives scant attention in its pages but is in the end what matters about him: his writing. I closed di Giovanni’s book and then reread with enjoyment the old Penguin Modern Classics edition of Labyrinths, that delight of my adolescence; then I sought out some unfamiliar essays from his collection The Total Library, including a beautiful and moving sequence of short pieces on Dante. It felt like taking a pleasantly cleansing bath. As a translator, di Giovanni no doubt served Borges well. As his biographer, frankly, he is taking the piss.