How vile the fashion industry is, and how tiresome it is always to have to pretend that it is fabulous and gorgeous and somehow magical. The truth is that under the froth - the unimaginably lavish parties, the beauty and the glamour - lurks a black, rotten core. Fashion eats people up and spits them out in a way that sends shivers down your spine: no wonder so many of its former shining stars end up unhinged.

Its defenders say fashion is an industry like any other and that brutality is an inevitable feature of any business, which is true enough - except that other industries aren’t peopled by fragile, eccentric, creative people like Isabella Blow, style queen and sometime fashion director of this newspaper, who killed herself last week, aged 48, by drinking weedkiller.

Blow was a stylist of genius, championed talent, and was possessed of great generosity (as well as the most fabulous figure in London). When she saw Alexander McQueen’s first collection, for instance, she bought the lot and agitated until he received the recognition she was sure he deserved. Until then, she let him live in her basement. Fast forward, and McQueen is a global brand, a squillionaire, and Blow is, well, dead.

And the industry she worked in and felt so passionately about surely had a part to play in that. Few of the fashion superstars she created and supported with every iota of her being ever thought to express their gratitude in a palpable sense and bung a few quid her way. Blow may have been posh but she was not rich, and was positively a pauper compared with her protégés.

Friends of Blow say that although she was motivated by everything other than financial greed, even she could not fail to notice, and eventually become troubled by, the enormous discrepancy in lifestyle and income between her existence and those of her protégés, many of whom became strangely elusive once she’d made them famous.

If she’d worked in any other business, she’d have been an agent or a headhunter and taken a commission for her pains. In fashion, biking round next season’s coat was considered an acceptable alternative. Blow needed a salary commensurate with her talents but never found a real corporate role for herself. Even fashion is populated with bland suits at the top, and the sad truth of the matter is that a woman with bleeding lipstick and a lobster hat is never going to be taken seriously in the boardroom, no matter how great her talent.

No wonder she was depressed. And no wonder, given the milieu in which she existed, that when she checked into the Priory last year everyone gossiped like mad but hardly a fashion soul went to visit her. Her sense of abandonment is said to have contributed to her jumping off a bridge on the way home.

Blow’s story has as extreme an ending as her sartorial style, but in these circles versions of it play themselves out quietly all the time. There is a branch of Alcoholics Anonymous in London where you can’t move for fashion casualties - not something those glossy articles about so-and-so’s fabulous lifestyle ever pick up on.

Someone I know, once so hot in fashion terms that Madonna tried to pick him up on the street in LA, also found himself weeping in the Priory recently; again, you could count his visitors on one hand. Not so hot any more, you see. You have to have exceptional resources if you work in fashion and the intelligence to recognise that the world that matters so much to you may be beautiful, irresistible, alluring, but it is built on illusion and pretence.

The handful who grasp this concept or, miraculously, remain unseduced by it, do very well. Those who were fragile in the first place and came to believe that being chauffeured everywhere, having not one but three personal trainers and being sent presents and lures by fashion houses on a daily basis somehow constituted the real world come a serious cropper when it ends overnight - as end it must - and they’re back alone in their grotty flat in Clapham.

No drivers, no parties, no tables at the Ivy, no presents, no tickets to the shows - oh, and the realisation that all those people who they thought were their best friends couldn’t care less about them. After years spent living in the fantasy world, the real one can come as the most debilitating shock.

Add to that fashion’s fixation with youth and you have a heaving cauldron of unpleasantness. We read and see a great deal about the love affair with youth - 13-year-old models and so on – but the really gruesome stuff goes on behind the scenes, such as the male designers who look completely freakish through excessive plastic surgery (I always wonder about this: if you can make the world’s most beautiful clothes, why can’t you see how unspeakably grotesque you look when you gaze adoringly into your own mirror?).

Then there are the ravages brought on by drugs and drink, and the eating disorders. A famously skinny designer recently took a shine to a friend of mine; once the show was over and everyone had left, the skinny designer took my friend into a little room and proceeded literally to ram handfuls of food into his own mouth, like a slavering animal. Not so chic.

And the sexual excess: a (male, straight) model was once working on a shoot with someone I know. It wasn’t going well; the photographer was grumpy. Everyone took a break and went for a drink, and the model was told to go up to the photographer’s room and “cheer him up” by having sex with him. He protested, as you would, but was told the contract would be lost if he didn’t comply. As he grudgingly went upstairs, everyone in the bar fell about laughing. Call me old fashioned, but it’s not really funny.

I love fashion, and I love clothes, and I admire and respect many of the people who work in the fashion industry. But enough of perpetuating the delusion that this is a charmed world populated by lovely people - and, by extension, a world we all wish we had access to.

The tributes to Isabella Blow in the papers last week were well deserved, but even in those she was depicted as little more than a great eccentric and a creature of fashion. She was more than that: she was a human being with thoughts and feelings that ultimately mattered more to her than all the hats in the world. It’s an ugly story - but then, it’s an ugly business.

india.knight@sunday-times.co.uk

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