I'm waiting at the dentist's when a man comes in with a little girl, a toddler. He's fortyish, dressed aggressively all in white - white shorts, white Aertex; even his greying hair has snow-white tips. With his neat, white terry-towelling socks (the type you buy in a value-for- money three-pack from M&S) and furred, muscly calves, he's the sort of man who slaps his thighs a lot, jingles his keys, and takes part in organised activities on Sunday mornings.

He acknowledges me with a faint upturn of the mouth, a genial crinkling of the flesh around the eyes. Then he chucks a rubber toy on to the floor. "Play with that," he instructs the toddler. Though abrupt, his voice is not unkind. Dogs, wives, secretaries, toddlers - he presumably addresses them all in the same brief, certain tone.

The female toddler obediently begins to manipulate the toy. The man shakes open the waiting-room Telegraph, stretches his legs and crosses them at the ankles. I return to my absorbed appraisal of Hello! magazine.

Then two more kids troop in from the surgery, clearly - judging by their submissive glances in his direction - fruit of the Man in White's loins.

"Well? How'd you get on?" he booms. "Get on all right?" He does not lower the newspaper, but speaks straight through it. I wait for him to blow a whistle, only it won't be like The Sound of Music - this man couldn't fall in love with a wayward nun if she jumped up and offered to iron his socks.

The boy is about eight, the girl younger, more like five. They're dressed identically in shorts and plain T-shirts, miniature versions of their father with their white socks and short, straight hair.

"Was it okay?" continues the father, "Did you have any pain or anything of that ilk?"

"Okay," says the boy. The girl says nothing.

"They were great," enthuses the woman at the desk. "Just great. I'll get them some stickers and balloons."

"Stickers and balloons?" queries the father. He lifts a hand dismissively. "Nah, we don't bother with any of that." No stickers and balloons? I am now very interested. I look up (from the photomontage of Princess Stephanie of Monaco's clinch-ridden honeymoon) to inspect the face of the man who will deny his children stickers and balloons.

"But?" the women already has her hand in her desk drawer. The children wait, eyes moving from one adult to another.

"I'd like one," says the little girl eventually in a tiny voice.

"You don't! You wouldn't," exclaims this Wandsworth Gradgrind, a smile on his face - and it's truly hard to decide whether he's joking. "What would you do with it? You'd lose it as soon as you got home."

Almost certainly true, I think. But since when were treats and rewards either cost-effective or useful?

The woman doesn't know whether the father's joking either. There's a moment of sheer embarrassment as she struggles to judge him, assess his type. "Just a sticker, then?"

The man sighs and shrugs exasperatedly, his patience eroded by the waves of ephemera crashing down around him.

The woman plants a bubble-gum scented (I know, my kids have had them) sticker on the little girl's chest. The girl pats it and glances involuntarily at her father. A tangerine sticker is planted on her brother's T-shirt. He steps back, embarrassed.

"Would your little sister like one?" asks the woman, now, getting into her stride - eyeing the baby greedily.

"Good God, no!" explodes the man, as if the child had been offered a margarita. "It'd be completely wasted on her."

"Balloons?" Pink-faced now with the effort of combat, the woman shoves a selection at the little boy. "Want one?" Forget the children - this is now a battle to the death. I know which side I'm on. I watch without shame.

But the boy hesitates, draws back. "We don't really bother with balloons," he says at last. Advantage Gradgrind.

My father didn't bother with "things" either. Neither especially clever nor even slightly original, he saw himself as a man of science, a sleekly practical man, a sort of unrecognised genius. Emotionally inadequate in every way, he sneered at anything remotely grey or uncertain or human and took refuge in the Black and the White.

He knew everything and believed in nothing. He could tell us the height of Mount Everest, the speed of sound, the spelling of "accommodation", "manoeuvre" and "diarrhoea". I knew from the age of six that PVC stood for Poly Vinyl Chloride. But he didn't believe in God or Father Christmas or the Tooth Fairy. He had no patience with Beatrix Potter or Mary Poppins, novels, poetry or any form of make-believe. The imagination was a dirty, foreign place and - you've guessed it - he never went abroad.

His own personal planet was an unadorned, amoral place, where actions had no consequences and you could behave as you chose as long as you didn't get caught. One of his favourite games was to slow down for hitchhikers and, just as they'd gathered up their bags and started to hurry towards the car, to speed away, laughing. We children ducked our heads in shame.

When he killed himself, his suicide note was left on the table next to his Co-op till receipt (whisky, baked beans, washing-up liquid) - his whole life contained in that list.

"Okay, team - out!" The Man in White and his kids file out of the waiting room. And I'm still trying to work out what I feel about the whole display when, just before pulling the door shut, rubber toy under his arm, he turns and gives me a wink of complicity.