Watching the new Dove ads, featuring smugly naked 'real' ladies of a certain age accessorised only by smiles and a snappy sell ('too old to be in an anti-ageing ad ... but this isn't anti-age ... it's pro-age ...'), I found myself wondering, idly, how much I would have to be paid to get my kit off in order to sell soap to people who would rather look at Kate Moss, and couldn't actually come up with a number with enough noughts. And, of course, the distressed viewers would have to be paid even more money in compensation.

This latest campaign is all about tackling the (buzz-phrase alert) Invisible Middle years, which is, basically, a spin on the late 20th century's middle youth, with added bingo wings. This is smart marketing because there are a lot of 40- and 50-somethings out there with potentially disposable wobbly bits, and enough spare time and disposable income to want to dispose of them without crunching, spinning or fung-schweeing [sic] their collective qi.

We are a truly self-deprecating generation, skilled at the sort of low self-esteem self-put-downs I shared with you in the first paragraph and which will doubtless pepper the rest of this piece. We can laugh at ourselves and our waistlines and our crap love lives and demanding jobs and horrible kids, and cheer ourselves up with a copy of Neris and India's Idiot-Proof Diet, laughing along with all the fine no-nonsense sisterly advice while working our way through a bar of Green & Black's.

We celebrate cellulite in public, curse it in private; diss our menfolk lovingly in public, weep into a pint of Chilean red in private; are proud-to-bursting of our kids when they reflect well on us in public, privately fantasise about infanticide in the frozen food aisle when, say, a cute man we suddenly, shockingly, realise is 10 years our junior fails, equally shockingly, to acknowledge our existence while we're both reaching for the baby broad beans.

Invisibility creeps up on you unawares. If you hit your forties child-free, Botoxed and with an ashtanga-ed arse, then you'll delay it a while, but it's still just a matter of time. Scrummy-mummies are also temporarily exempt - nothing gets a bloke hotter under the collar than the sight of a woman whose reproductive organs are clearly up to scratch but who still looks as though she spends evenings lap-dancing instead of lactating. But if you're a breeder of the elderly gravida variety, you'll already know exactly what I mean. Yes - brave smiles aside - even those women in the Dove ads.

Now I haven't got It any more (skin without crows' feet, thighs that don't look like a bag of marshmallows wrapped in rubber bands, pearly whites, a sense of humour that isn't confined to the written word and an ability to believe, against the odds, in the existence of Mr Right ...), I wish I'd enjoyed It all a hell of a lot more when I did.

These were the years during which I used to joke, in all seriousness, about looking better naked than dressed (how we girls laughed!) but still agonised endlessly over what now seems like pointless trivia (but why won't he call?). That youth, and waists, are wasted on the young is a given, but that doesn't mean it won't hurt when we're finally grown-up enough to understand why.

And even though, on brighter days, I am woman enough to look at the stretch marks that adorn the spare tyre which is on top of my love-handles and think of the collateral damage as a badge of honour - the purple hearts of child-bearing - more often the sight of my unadorned flesh makes me realise there isn't an anti-ageing product on earth with enough science to bring back that youthful confidence. And as for looking better naked than dressed ... well, I don't know when that ceased to be the case, precisely, but I'm pretty sure I can't blame the kids.

These can be difficult, transitive years because they inevitably coincide with an inability to let go of the past and an unwillingness to face up to the future. I know enough attractive confident successful older women to know that social gatherings in one's fifties and sixties needn't mean donning a paper bag and retiring to a window-seat to ease the old osteoporosis, but I also know that I've got a bit of work to do before I'm ready to start subscribing to Saga and addressing police officers as 'young man'.

I have a vision of the rest of my forties which is two parts Easy Living magazine to one part One Foot in the Grave. I detect early-onset Victoria Meldrew syndrome every time I tut-tut over loitering teens in hoodies, or the c-word on the telly, or white-van man cutting me up at the lights (recording another series of Grumpy Old Women is more fun each year), but I also have a yen for underwear that is pointlessly, self-indulgently glamorous, and shoes with heels that hurt, and for a compliment that doesn't kick off with 'you look well!', or (and I'm pushing my luck here) even a wolf-whistle from a fit scaffolder half my age - albeit with cataracts. Though I'd settle for the you're-not-all-that-frankly bloke in the frozen food aisle to maybe meet my eye instead of staring through me.

But my youngest son is only nine months old and by the time he's a teenager I hope to be a right old Mrs Robinson, in cashmere, designer wellies and Agent Provocateur (not necessarily all at the same time), mixing my V&T in a kitchen with poured concrete work surfaces, surrounded by my best girls laughing at jokes about being as handy with a Rabbit as we are with a screwdriver.

Obviously this would be a major triumph of hope over experience but I wouldn't be the first middle-aged woman to dream of a perfectly Visible Middle. In the meantime, however, I'll almost certainly be buying a lot of cleverly marketed soap.