She is in her thirties, with many of the trappings of affluent middle age - the mortgage, the carefully tended roof terrace or garden, the designer clothes and possibly a Gap-clad child. But, suspended, as one PR woman put it, somewhere between E and HRT, she also unashamedly pilfers from the fabric of 20-something life. She goes weekend clubbing where she and her friends occasionally indulge in Class A drugs, although she's usually home in time for a few hours' sleep before a visit to the garden centre. She just about knows the difference between techno and drum 'n' bass and her CD collection has the latest from Radiohead and The Verve among the Frank Sinatra and Van Morrison. She loves Friday night television on Channel 4 and she is deeply dismayed that there is to be no third series of This Life.
He is also in his thirties, a Nick Hornby-esque middle man, straddling the divide between Loaded laddery and DIY maturity, a lager-damaged liver and prostate trouble. And he's remarkably similar to her.
They are Britain's middle children - younger than the post-war Baby Boomers, older than the Chemical Generation, for whom Ecstasy- influenced dance culture is the defining social characteristic. The Pepsi generation is old enough to know better, but remains intent on combining the adrenaline-charged excesses of youth culture with the comforts of middle age. They certainly never act their age.
The marketing people, the advertisers and the sociologists have been watching Mr and Ms Middle Youth from their glass offices for a while. After all, there is nothing mysterious about the trends that have paved the way for the Pepsi generation - a decline in two-parent families and in marriage, delayed childbearing, improved health and longevity, beauty products and exercise routines that have delayed the onset of wrinkles and flab. But it was the research for a new women's magazine, Red, that was to crystallise a vague sense that there was another type of 30-something consumer - one that might be middle in age, but was not yet middle-aged - into a macro-social trend which has an instant resonance for Nineties' Peter Pans.
Moreover, the concept has one distinct advantage over 1980s social groupings. Whereas being a Yuppie carried with it a pejorative edge of cultural and consumerist vulgarity and being a Sloane usually meant you were a couple of pearls short of a choker, almost everyone over the age of 29 wants to be a part of the Pepsi generation.
IF there is a human archetype for Ms Middle Youth it is Kath Brown, editor of the embryonic Red magazine, which launches in January. "Me and my friends," she says, in answer to the question of who mid-youthers might be. At 33, she easily reconciles her home-making urges with the desire to go to the Glastonbury festival, her love of cooking and gardening with a lust for reckless youths portrayed by the likes of Ewan Macgregor, her mortgage with the absence of a gene for maturity apparently afflicting her generation.
"It's an attitude thing," she explains. "It is about accepting all the responsibilities that come with growing up, but not being a 'grown up'." Accordingly, Red magazine has been conceived to fill the chasm between Cosmopolitan and Good Housekeeping.
As an advocate for her niche market, Brown is convincing. "Basically, we like ER, Friends and, definitely, This Life," she says. "We don't mind getting muddy in a field for a music festival, although we would be more likely to spend a bit of time and money on a bottle of wine than just drink something which got you drunk cheaply. We were probably punks or hippies in the late Seventies or early Eighties so rejecting traditional values still comes easily, but we now shop in Habitat, Nicole Farhi and DKNY. More than anything, we are terribly busy," she adds in the harassed tone of a woman who is on the verge of a magazine launch.
Brown, who lives in North London with her cat, Ginger, is not married, although she is "sort of considering it" and she doesn't have children, although she thinks most middle-youth people probably do ("it's just that their children haven't made them grow up"). Health and body maintenance are preoccupations, although mid-youth Woman knows that diets don't work. They are sexually adventurous, although single mid-youthers don't have enough time or left-over energy to be as wildly promiscuous as they might like, and partnered mid-youthers have given up Cosmo-worries about how to have 50 different types of orgasms.
She is reluctant to state how mid-youthers interact with the so-called chemical generation, because "I don't want to make out our target audience are a bunch of drug-takers", but she says that a Red woman would not be shocked if one of her friends were to take drugs at a party. "Rave culture has been a huge influence on this whole generation because most of them will have experienced it in their twenties," she says. "The best thing about being a mid-youther is you no longer have to feel embarrassed about going clubbing in your thirties. So many other people are doing it as well - you don't have to feel like you're the oldest swinger in town."
But there is an inherent danger with trendspotting by media types. Most people involved with writing, publishing, broadcasting, advertising or promotions are middle-youth by definition - being aware of the latest trends is practically part of the job description. If everyone in medialand is jumping up and down shouting "That's me!", isn't that because, in seeking to define a cultural phenomenon, we have actually managed to define ourselves? The success or failure of Red magazine may answer this question.
Meanwhile, the reader profile is primarily consumer- rather than value- centred, by its very nature. (Mid-youthers are frequent travellers, especially to European destinations; they love Tesco Metro and Homebase; and they are likely to be lapsed vegetarians.) Yet, most interesting of all are the politics of the Pepsi generation because they are so in tune with the youthful new Prime Minister. These affluent liberal professionals are the backbone of New Britain - the left-of-centre equivalent of the Yuppie children who bought into Thatcherism so wholeheartedly in the 1980s. Tony Blair may be a classic baby-boomer, but he is also an accidental icon for Middle Youth - with his invitation to Number 10 for the Gallagher brothers, his guitar-playing and his chunky-knit-sweater, 'call-me-Tony' familiarity.
According to polling evidence from MORI, 42 per cent of middle-youth men and 45 per cent of middle-youth women voted Labour at the general election. They are an issue-minded subsection of the population, with 25 per cent saying they are a member of a charity or a political organisation; 60 per cent have recently given money to one. They are the most pro-European social group: more than 50 per cent believing Britain should be a part of Europe and most are in favour of a common European passport.
The drug use of the group is minimal, with under 3 per cent using Ecstasy, cocaine and amphetamine "nowadays"; 14 per cent use cannabis. But a higher proportion say they have friends who use all these drugs, indicating they are probably spending time with people in the younger and higher drug-use bracket.
The inherent schizophrenia of the group is apparent through the MORI figures. This, after all, is a social grouping which has a great deal in common with the age-group below it, but also represents a constituency within which 30 per cent of people have recently made a very un-rock 'n' roll visit to a National Trust house or garden. Peter York, the social commentator who once brought the world the Sloane Ranger, says this breadth of lifestyle choices is exactly what defines the Pepsi generation.
"They quite simply want more of everything," he says. "There was the age of this and the age of that, and this has basically become the age of this and that - which is great news for people who want to sell things. Life-cycle generational experiences are, at last, up for grabs."
Do these 10 tell-tale signs sound like you?
1. Your 29th birthday has passed, but you feel you're still waiting to grow up.
2. You listen to Radiohead when you pick your kids up from school.
3. Your weekend usually includes a night's clubbing and a trip to the garden centre.
4. You went to this year's Glastonbury festival, even if you couldn't quite face staying under canvas.
5. You think Tesco Metro was designed especially for you.
6. Your ideal Friday night is watching Channel 4.
7. You considered telephoning the BBC when you heard there would be no third series of This Life.
8. You find that a night out taking Ecstasy has become too debilitating because you've got too much to do the next day.
9. You have smoked cannabis, but nowadays finding a dealer is too much bother.
10. You cook from the River Cafe Cook Book, but sometimes only Pot Noodles will do.