I ARRIVE at Osla's parents' home, an old farmhouse in Chilton, County Durham, to receive some surprising news. Osla, her mother Sally tells me, is in the shower, making herself presentable for me and the photographer. Perhaps it's all a ruse, I think, already doubting what I've heard of her crimes against cleanliness and more than willing to suspect television of exaggeration. The impression is strengthened when the girl herself emerges, casually but respectably dressed in jeans and a T-shirt, without make-up, but without needing any.

The granddaughter of a diplomat, Osla, 23, is named after her paternal grandmother, once a close friend of Prince Phillip. The prince is her uncle's godfather, although the family's royal connections have now been mainly lost.

Yet far from embracing the trappings of her heritage, spending a fortune on grooming and designer clothes, Osla admits she has never cared much for how she looked. "I've never been one of those girls who's into my appearance. At boarding school, one of my friends would get up and do her makeup routine but if there was more sleeping time, I would make all attempts to try and stay in bed," she says.

Having started as "not a particularly mucky child", being given regular baths by her parents, Osla says things began to deteriorate during her school years, first at Redhouse, in Norton, near Stockton, then Barnard Castle School. But it wasn't until she started university, initially at Nottingham, that things really went downhill.

Without a shred of embarrassment, Osla reveals that so slovenly were her habits, fellow students dubbed her "The Ming". "I think probably my worst period was my first year at university - I think I got a bit of a reputation then," she says, grinning sheepishly. "My room just smelt - I don't know why. It was normally somewhere that people wouldn't go into. I had other priorities than cleaning." Without revealing the horrors that lay therein, she does insist: "There wasn't food everywhere, or anything like that."

Osla claims that one of the main stumbling blocks was the difficulty in washing at her halls of residence. "Washing was always a bit of a mission because our washing machine was right down at the bottom. You had to wait in a queue and it would be an all-day thing," she says.

Which is why, she doesn't mind admitting, it was easier to just not bother. And far from providing an incentive, the fact that she had a boyfriend only made her less assiduous. "I was going out with someone for most of that year and I got a bit lazy," she admits. Didn't he mind? "He was a bit grungy," she explains, nonchalantly.

When Osla changed course and university, moving to Leeds to study French, she took her grubby habits with her. "I'm not very good at washing sheets - I can't remember the last time I washed them. It's just easier to wait until you get home," she says.

Not even a holiday job as a waitress with a catering firm in Nottingham has managed to reform her - although she says she never actually turns up to work dirty. "The boss usually makes a comment about the scrumpled nature of my shirt and despairs a bit, but it doesn't really make a difference," says Osla.

She got involved in Too Posh To Wash after she and some friends were stopped by researchers for the programme in Nottingham and her friends couldn't wait to nominate her. Within weeks, Kim and Aggie were filming at her parents' home. Osla says: "Kim and Aggie were like pantomime dames. I really liked both of them but they do have cleaning problems. They both really are cleaning obsessed."

Which Osla clearly isn't. But so far, I've been unable to decide if she's just a normal scruffy student, as she seems to think, or someone more seriously scummy. When she describes what the grime-fighting duo unearthed, I must admit to veering towards the latter.

"There was a bra that I had which got taken away for testing and was never returned because they found 80 million bacteria or something like that," she says, adding: "But then again they do multiply, so I'm thinking it's not that bad."

She also had her teeth examined and was bemused when the remnant of a brace was found. "I had glue stuck on my teeth from the year before, when I had a temporary brace. I was supposed to go back and have the glue taken off but I forgot all about it. All the bacteria had collected on it and I had 15 times the normal amount," says Osla in typical laid-back fashion.

On an equally disturbing note, she admits to sometimes forgetting to wash and change her clothes - "When I've thought about it, it's been a couple of days since I've washed and I'm in the same clothes. It slips my mind," - and wearing her knickers for two days, turning them inside out for the second wearing, although she says she does this "only on extreme occasions".

To teach her the error of her ways, Kim and Aggie took her first into Durham, where people were invited to smell her - "they were quite polite," she says - then into Consett, where she suffered the indignity of having to wear a dressing gown with "soap dodger" on the back.

But the worst part, says Osla, who admits to not being "an every day shower person", was being given a decontamination shower by the lake near her parents' house. "It was probably the most traumatic bit of it," she says.

While Osla seems indifferent to her impending fame for being filthy, her mum Sally is a bit more concerned - although admittedly, not unduly. "I know there are going to be a lot of mothers who watch this TV programme who will say, 'I wonder what her mother was doing when she was growing up,' but I did teach her how to use the washing machine and things like that - she just didn't listen. Mothers can't win," she says with resignation. As further proof of her diligence, she points out that Osla's sister Ruth, 18, is fanatical about grooming and even her brother Tom, 21, makes an effort.

But has Osla learned from Kim and Aggie's instruction? She claims she has. "They do know what they're talking about and I have learned some things," she says. "After the show, I got myself some new clothes and I think I've managed to clean myself up a bit. I've also got some hair straighteners."

So, she wouldn't mind if I had a quick inspection of her room then? Osla is happy to lead me up the stairs, past a wall with peeling plaster, to her attic bedroom. Am I assaulted by sights and smells to send even the most hardened student fleeing in horror? Not really, although it's not a pretty sight. The bed is unmade and the floor is strewn with Osla's wet towel and clothes but there's nothing repugnant here - except, perhaps, the discarded knickers. I emerge unscathed and ready to embrace the sanitised order of my own world.

l Too Posh To Wash begins on C4 next month