'I want it 110%'

Dawn breaks over the luxury mansions of Camps Bay, Cape Town, South Africa and the air is already acrid with whining and bitchery. Britain's Next Top Model, Living's high-tension hunt for the new Kate Moss, arrived in town last night for its grand finale, carting four remaining contestants in petulant tow.

Models in training, Alex, Rachael, Catherine and Stefanie, have been trapped together and fly-on-the-wall "reality" filmed for the past 10 weeks now. Any love between the rivals was lost many mascara wands ago. "I just want to be Britain's Next Top Model! I want it 110%! I'm so focused! Because, y'know, you only get one life! You have to live it to the max!" explains Rachael Cairns, 19, a showbizzy Sylvia Young-trained brunette, almost breaking into a hot shoe shuffle as she chirps.

In the background, sky-scraping redhead Catherine Thomas, 19, the most obvious "model" of the four, pulls "mouth sick explosion" faces. Meanwhile doe-eyed Alex, 18, crop-haired, cocky, believes size zero is "beautiful cos you can't send heifers down the catwalk" and mutters something uncharitable about Rachael being "like a performing monkey". Over in a far corner of the multi-million pound model mansion Stefanie, 22, a simmering Latino-type with a mid-sized bosom simply sighs at Rachael's latest "off the cuff" performance. Stefanie, a neat size 10, is this year's "bigger girl", continually taking flack from the other girls and judges for being "too glamour model" and giving her poses too much "sex" in an industry where the ability to jam one hand on a hip androgynously in a "look I'm being a teapot" pose while channelling a Vulcan death glare is endlessly celebrated. In their real life, up close, non-airbrushed state there isn't one of these women I'd rather look like or be. The magazine version, however, is another soul-sapping matter entirely.

The thing about Britain's Next Top Model is that you either buy into the glitzy premise or you don't. You either believe with great gusto that we're finding supermodels here and making dreams come true and this is a good thing or you're a naysayer who just shouldn't watch it. Dozens of my friends love BNTM. They take umbrage at my Emperor's New Clothes remarks about the silly tasks ("Ooh it's LisaMail! We've got to climb a rope ladder in a monsoon holding a basket of kumquats!") or the "top fashion industry experts" trollied out to impart bon mots to the girls ("Ha ha! Expert!? That's just someone with a clothes shop who's agreed to lend free frocks! What does he know? Anyway, if they're beautiful enough to be models, why don't they just pitch up at Storm and get signed with an agent?" Response: icy silence, scored off Christmas card list irrevocably).

Season or "cycle" four of the show - with all-new judges Huggy Ragnarsson and Gerry DeVeaux - didn't win me over either. Honestly, I want my heart to boom with joy when the glorious Lisa Snowdon magics up like Miss Popov with a little challenge for the budding covergirls, but then I watch episode one where the 14 girls are whisked to a basement carpark at 6am where Julien from Models 1 shoves Polaroid cameras in their hands and makes them snap photos of each other's worst feature. Alex, who is a dress size six, is told she has flabby arms and "muffin handles". Elsewhere, tiny waists, bums, thighs and faces are rejected as fat. Some don't want to play the game any more but are told that if they don't get this important lesson they're are failures who can never succeed.

Afterwards the footage is spliced together with music and whizzy effects and melded into an addictive, glossy, brain-chuddy reality show and stuck on telly on endless repeat for girls to enjoy alongside America's Top Model and BBC3's Find Me The Face and Five's Make Me A Supermodel. Then, six weeks later, I watch BBC1's Child Of Our Time and see footage of eight-year-old girls being quizzed about body image. One after one the little slender innocents traipse into the controlled experiment and waffle about being fatter than they should and how it makes them sad, which is interesting because that's how almost every one of my grown-up female friends feels too.

"But this has been my dream, honestly, since I can ever remember. I've focused on it and stayed true to myself. I think if you follow your dreams and keep it real they can come true. I want to be a model so much," Alex tells me earnestly, in an arduous head-to head which sends me off with a notepad full of "empowering" soundbites perfect to sell Lucozade. It's not easy to draw the girls on anything other than "their journey" and "keeping it real" and how anything a bit crap is "making them stronger as a person".

These days, I love being around reality TV stars mid-shoot because their brains are so locked on being their "character" it's like living in a postmodern hinterworld much like ITV1's Moving Wallpaper. During the BNTM's South African Warrior Shoot, I watch the girls wander into rooms, and make smalltalk with each other about make-up and dresses, but then the moment a camera is shoved in their face by a nosy producer, without any prompting whatsoever, they'll turn on their heels, leave the room and return to do the entire speech again, word perfect, but this time louder and more "telly" with breathless squeaks and whirling dervish hands. Rachael is the biggest culprit. Oh and crying too: oceans and oceans of tears at the mere whisper of being sent home and resuming her other career, as, ahem, an actress who's appeared in Robin Hood, Doctors and Casualty. After 10 weeks of rather disingenuous snot, everyone is tired of her.

As the girls arrive at today's location, a Cape Town church hall, to meet Lisa and the judges, view their "best shot" and hear who goes home, a great rumpus is brewing between the producers and the girls with regards to "cheating". It happened two days ago, apparently. It seems Alex prompted Catherine with her lines when they were filming the abseiling commercial task. Weirdly, none of the 45-strong crew stood on the side of that hill noticed it at the time; now, five minutes before filming begins today, the girls are told the grave seriousness of their vile dishonesty. Obviously, a tsunami of tears follows, with producers hugging girls sympathetically and girls croaking apologies about how devastated they are that this might wreck their "journey". It's a dead heat between who is fooling who here, but it's creating great telly.

Now with tension cranked up to 11, it's time to film the goodbye part. As the cameras roll, the model who's slung out weeps desolately throughout the process, begging mercy from Queen Lisa to fight another day. Sadly, she's had her chips though (metaphorically of course, perish the thought) and is told to leave. The girl howls all the way out of camera view, all the way behind the screens, all the way to the ante-room, where suddenly - hey presto! - she is completely normal again, aside from crocodile tears which she dabs with a tissue while informing people to inform me that she'll be available to do press in two hours. To be honest, I'd love to say I was at all shocked, but I'm all about "keeping it real"

· Britain's Next Top Model final begins Mon, 9pm, Living