Why do people in shoe shops pretend your feet have shrunk while they were in the stock room?

Thursday lunchtime: the Tube is full of sallow-skinned, dandruffy men in shiny suits who stare at me as I eat my sandwich, even though I do it with dignity, chewing delicately and keeping my lips together as I've been taught.

When I was 13, my mother decided I should learn some table manners. Each family mealtime I had to eat in front of a mirror, her tilting, pine dressing- table mirror, placed in front of me at the end of our refectory table. My siblings, all faultless eaters, thought it was very funny.

But I gazed into the mirror and learnt to see nothing. My revenge was that I dreamt of other things. The large dark oblong cut me off from the rest of the family and, once my lips were behaving themselves and it was removed, I almost missed it.

I get off at Sloane Square, ostensibly to catch a bus home, but I find myself instead in Patrick Cox's new Wannabe store. There's something slinkily, memorably hypnotic about that word "wannabe". Now I'm dazzled by expensive glass in the weak afternoon sunshine. Frantically aimless as a moth, I enter.

The window contains a sober selection of mock-croc loafers and some furniture covered in mustard and lime flowery fabric, the sort you'd find in the Seventies sun loggia of your frumpiest great aunt. But the shop is (of course) the height of Post-Modern chic. No one smiles, everyone looks tired. There are a lot of shiny surfaces.

A girl with long blond hair and a totally concave belly is trying on some high-heeled white loafers. She stares and stares at her feet in the mirror and I stare, too. Such tiny, perfect feet, a size four I'd guess. My own are virtually off the end of the scale at size eight and have been since I was about 13 (yes, big feet and bad table manners).

"Yes," the assistant slouches over.

I finger a pair of lipstick-red loafers. "Would you have these - in an eight?

"Very much doubt it." He glances down at my scuffed and yellowing trainers, which never truly recovered from the sea at Dunwich two summers ago. "But I'll see."

The blonde girl continues to watch her perfect reflection. Her hip-bones stick out just over the front of her jeans (I'm not exaggerating). It's a polished slalom of a body. I try to decide whether it's attractive or freakish. She pouts, looks down and delicately picks a long blond hair off her black turtleneck.

The man comes back. I realise he's dressed just like Marty in Randall and Hopkirk (Deceased) - ghost-white suit, odd, brushed-forward hair, ankle boots. "Sorry," he says, "but here's a seven."

Why do people in shoe shops like to pretend that your feet may have shrunk magically in the three or four minutes they were in the stock room? If my feet suddenly measured seven now, after so many years, I'd probably seek medical help. I dish Marty a curt negative and leave, relieved to have been delivered from temptation.

Back home I decide it's time to make the best of the down-at-heel, unpolished shoes I've already got, so I take my old, but still convincingly classic, brown boots to the mender's. I've known the cobbler for several years. He used to be in the shop across the street, but recently left and set up on his own. He has a daughter the same age as mine.

He cradles my boots in his hands, feels the leather, inspects the soles, flexes them respectfully between his fingers. "Old?" he asks me.

"About 10 years, actually." They were expensive, a present from an old boyfriend. We split up and I tossed them disdainfully in the back of a cupboard. Five years later, I sneakily discovered I could face them again. They've trudged through snow in New York, across windy English beaches and up and down wet and gritty Clapham High Street. Good shoes last longer than love.

"So how's business?" I ask him.

"So-so," he shrugs, then adds portentously, "but Pizza Express is coming." He motions down the street to where red and yellow boards clapped on to what was the old charity shop announce, "Acquired for an exciting new eatery." I have a vision of people eating Venezianas in their stockinged feet while my friend provides a While-U-Eat mending service three doors down.

That night, oddly, I dream that a stout and mannish old lady in country clothes invites me to her house for some pizza and bossily insists that I put on a pair of Peter Rabbit's little brown shoes. She tells me she's Beatrix Potter.

"Then why are you eating pizza?" I ask.

"Because Pizza Express has arrived."

Suddenly her cottage is suffused with King's Road types dressed in spangles and velvets and blue nail polish and Patrick Cox shoes (the high-heeled velvet and diamante ones). I feel a frump in slip-ons, which everyone knows were most recently seen discarded in Mr MacGregor's garden.

Beatrix produces a bottle of vodka and some funny-looking cigarettes. I tell her I'd love to stay but I've got three children to deal with in the morning, plus work, Sainsbury's and school runs.

"Just listen to you," she snaps, and I notice with alarm that there are prickles poking through her paisley bodice. "How can you expect to graduate to funky shoes if you're not prepared to stick your neck out and party?"

I am about to protest when the prickles recede and I wake in my own bed at 7.15am as usual, with Jacob flumping about on my legs saying, "Shall I tell you a few facts about the Tudors?"