This spare tyre has blown fashion apart

I'm halfway there: these days I only "dress up" if I'm going somewhere and school/the pub/lunch with a friend don't count. But milling about town in my "home" clothes, as I often do, I can't help but be taken aback by the incredible sartorial lengths "ordinary" - by which I mean busy, hard-working, short of time, not rich - women go to on a daily basis. Surely this is a newish thing, wandering about waxed, primped, hoisted, hoicked, tottering, just to go to the office or do the school run before a stroll round Morrisons?

I was in Oxford Street in London for hours last Thursday night, trying to find a suit for my 16-year-old son, and I observed dozens of these women: knackered from a day at work, at 8pm in the evening, still in their painful heels, structured dresses, accessories, handbags, face full of slap. I was wearing flip-flops, leggings and a giant cardigan. I may have looked like a potato, but the horror of traipsing around this unloveliest of streets was mitigated by at least being able to exhale, or indeed walk, without causing myself pain.

I love fashion and I admire it. The forthcoming film The September Issue - a documentary that follows the putting together of American Vogue's, er, September issue - sounds like it ought to be some kind of real-life Ab Fab laughathon, starring Anna "Nuclear" Wintour, the magazine's editor, but is in fact a film about uniquely talented people, Grace Coddington chief among them, making art and fashioning dreams.

The putting together of a shoot inspired by the photographer Brassaï, in particular, is shown to be a serious piece of artistic creation: it isn't funny or silly or weird - just amazing to watch and an act of pure creativity, like painting or sculpting or writing music. What the film underlines is the giant chasm between high fashion and the high street, or between striking creative talent and what passes for fashion knowledge in everyday life.

The stupid version and stupid fashion's stupider preoccupations are, inevitably, the ones that get coverage. The size of models, for instance. There's been a hoo-hah going on about Lizzie Miller, an American "plus size" (she's a UK size 12) model whose photograph featured in the pages of the US edition of Glamour magazine. Miller was naked and a tiny roll of stomach fat was visible. The picture the magazine used wasn't large and it appeared on page 194. Nevertheless, a veritable clamour ensued.

Cindi Leive, Glamour's editor, said: "The letters about it started to flood my inbox the day [the issue] hit the newsstands. I hope it's the beginning of a revolution."

"I am gasping with delight ... I love the woman on p194," one reader wrote. "A real woman who looks like a person!" another commented. "She makes me want to go out to the rooftop and shout."

The whole thing is completely weird. If Leive really does hope for "the beginning of a revolution", then all she has to do is use bigger, more normal-looking models. (She won't.) If the magazine's readers really do feel like throwing street parties to celebrate the appearance of half an inch of normal fat in the pages of their glossy magazine, then all they have to do is relax and stop judging other women. (They won't. They are happy - crazed with joy - with the half-inch of fat in novel isolation; they wouldn't like it on every page.) The reason magazines are crammed full of the super-skinny is that women, despite what they may say in public, like the fact that the £2,000 dress is being modelled by someone who's 14 and a size 4 (even though back in the real world, where obesity is rampant, you're more likely to come across a four-year-old who's practically a size 14).

I've thought for years about why this should be. Fashion is smoke, mirrors and artifice: we all look at clothes we can't afford, styled in a way we could never recreate, and we like doing so only because nothing in the picture bears any relation to real life - it's all a lovely dream. We can't afford the dress and anyway we don't have the kind of life for the dress. We can't do our make-up like that or our hair. We'd fall over if we tried on the shoes. As for the girl - well, she's the least real thing of all. We could never be like her. But it's all beautiful and reassuringly unreal.

Add an iota of reality - a size 16 model, say - and the whole thing falls apart. It's no longer bliss to look at. The average British woman is a size 16; now she's looking at the picture and thinking: "I don't look like that. Why don't I look like that? She doesn't have cellulite. Why do I? Where's her double chin? She's so pretty. I'm not." It's not fun: now the reader feels bad, cross, plain. She's technically a bit like the girl in the picture, but miles away in reality.

Fashion surely ought to be about joy and it very seldom is. There was nothing joyous about the buniony frock-slaves on Oxford Street last week. It ought to be about happiness and creativity, but women sitting in sartorial judgment on other women is about unhappiness, delusion and insecurity. It used to be fun and it's not any more: something's gone awry.

The revolution will come when women decide that enough is enough and wear what they like - whether it's the height of fashion or a moth-eaten cardigan - weigh what they like, whether it's slightly too much or slightly too little - and stick two fingers up at the whole nonsensical tyranny. That doesn't mean you can't appreciate fashion or swoon at the loveliness of the pictures in Vogue - but it does mean it's probably okay to venture out of the house occasionally without the 3in heels and waist-shrinking pants.

+ I am triumphant and I shall crow. I've never helped my teenage children with homework, never rewritten their essays, never even ensured they do their prep: I have faith in the quality of their education and, as far as I am concerned, learning that actions have consequences (such as detention) and that work pays dividends (good marks) is a valuable life lesson.

Whether my non-cosseting (to put it mildly) style worked or not was always going to be demonstrated by my eldest son's GCSE results on August 27 and I did have a couple of sleepless nights beforehand wondering whether my whole approach hadn't been a terrible mistake and whether a little spoon-feeding wouldn't have gone amiss. Then the results arrived and lo, they were good - which wasn't a given, considering the minuscule amount of revision involved (I was in a terrible panic about this from late May onwards, to no avail: it's impossible to force someone who's taller than you to sit nicely with his Virgil).

You may recall that I wrote about how someone I know had informed me, a few months ago, that I was "the only parent" she knew who wasn't having her privately educated child tutored for GCSEs and about how the very idea of this had sent me into a fury.

Well, ha, is all I can say. HA!