Not everyone knows what it is to have your father’s rival’s penis inches from your nose

That stale, uncertain voice. My entire life I’ve endured the twin torments of his whistling and his speaking. I’ve been spared the sight of him, but that will soon change. In the dim-lit gore of the delivery room (Trudy has decided that he, not my father, will be there), when I emerge to greet him at last, my questions will remain, whatever form he takes: what is my mother doing? What can she want? Has she conjured Claude to illustrate the enigma of the erotic?

Not everyone knows what it is to have your father’s rival’s penis inches from your nose. By this late stage they should be refraining on my behalf. Courtesy, if not clinical judgement, demands it. I close my eyes, I grit my gums, I brace myself against the uterine walls. This turbulence would shake the wings off a Boeing. My mother goads her lover, whips him on with her fairground shrieks. Wall of Death! On each occasion, on every piston stroke, I dread that he’ll break through and shaft my soft-boned skull and seed my thoughts with his essence, with the teeming cream of his banality. Then, brain-damaged, I’ll think and speak like him. I’ll be the son of Claude.

But rather trap me inside a wingless Boeing’s mid-Atlantic plunge than book me one more night of his foreplay. Here I am, in the front stalls, awkwardly seated upside down. This is a minimal production, bleakly modern, a two-hander. The lights are full on, and here comes Claude. It’s himself, not my mother, he intends to undress. He neatly folds his clothes across a chair. His nakedness is as unstartling as an accountant’s suit. He wanders about the bedroom, upstage, downstage, bare-skinned through the soft drizzle of his soliloquy. His aunt’s pink birthday soap that he must return to Curzon Street, a mostly forgotten dream he had, the price of diesel, it feels like Tuesday. But it’s not. Each brave new topic rises groaning to its feet, totters, then falls to the next. And my mother? On the bed, between the sheets, partly dressed, wholly attentive, with ready hums and sympathetic nods. Known only to me, under the bedclothes, a forefinger curls over her modest clitoral snood and rests a sweet half-inch inside her. This finger she gently rocks as she concedes everything and offers up her soul. I assume it’s delicious to do so. Yes, she murmurs through her sighs, she too had her doubts about the soap, yes, her dreams are also lost to her too soon, she too thinks it’s Tuesday. Nothing about diesel – a small mercy.

His knees depress the unfaithful mattress that lately held my father. With able thumbs she hooks her panties clear. Enter Claude. Sometimes he’ll call her his mouse, which seems to please her, but no kisses, nothing touched or fondled, or murmured or promised, no licks of kindness, no playful daydreams. Only the accelerating creak of the bed, until at last my mother arrives to take her place on the Wall of Death and begins to scream. You might know this old-fashioned attraction of the funfair. As it turns and accelerates, centrifugal force pins you against the wall while the floor beneath you drops giddily away. Trudy spins faster, her face is a blur of strawberries and cream, and a green smear of angelica where her eyes once were. She screams louder, then, after her final rising-falling shout-and-shudder, I hear his abrupt, strangled grunt. The briefest pause. Exit Claude. The mattress dips again and his voice resumes, now from the bathroom – a reprise of Curzon Street or the day of the week, and some cheerful assays on the Nokia theme. One act, three minutes at most, no repeats. Often she joins him in the bathroom and, without touching, they expunge each other from their bodies with absolving hot water. Nothing tender, no fond dozing in a lovers’ tangled clasp. During this brisk ablution, minds swabbed clean by orgasm, they often turn to plotting, but in the room’s tiled echo, against running taps, their words are lost to me.

Which is why I know so little of their plan. Only that it excites them, lowers their voices, even when they think they’re alone. Nor do I know Claude’s surname. By profession a property developer, though not as successful as most. The brief and profitable ownership of a tower block in Cardiff was one peak of his achievement. Wealthy? Inherited a seven-figure sum, now down, it seems, to his last quarter-million. He leaves our house around ten, returns after six. Here are two opposing propositions: the first, a firmer personality lurks inside a shell of blandness. To be this insipid is hardly plausible. Someone clever and dark and calculating is hiding in there. As a man he’s a piece of work, a self-constructed device, a tool for hard deception, scheming against Trudy even as he schemes beside her. The second, he’s as he appears, the cockle has no morsel, he’s as honest a schemer as she, only dimmer. For her part, she’d rather not doubt a man who hurls her over the gates of paradise in under three minutes. Whereas I keep an open mind.

Ian McEwan, Nutshell, 2016.