If I had spent half as much time in my life studying Shakespeare's texts as I have analysing Joni Mitchell's lyrics, I would probably be a university professor by now. It is no exaggeration to say I am obsessed with her work, her words in particular, and most especially the 1975 masterpiece that is The Hissing of Summer Lawns.

Anyway (and there is a point here), there are some lyrics on that album that have slightly puzzled me since I first bought it when I was 16. They're in the song Sweet Bird, which even back then, when I had thighs as smooth as marble and a jawline as firm as a football, I understood to be about ageing.

It was this passage that always tripped me up:

"Sweet bird you are, briefer than a falling star All these vain promises on beauty jars..."

Surely, I thought, someone as intelligent and insightful - not to mention beautiful - as Joni Mitchell would never be so dumb as to fall for the idea that you could rub something onto your face and then look younger...

That all came back to me this morning as I surveyed my bathroom shelf, trying to find my neck cream, among the small city of potions, lotions, elixirs and serums I have accumulated, trying desperately to cling to the fading tail of the falling star of my own youth.

It's a new thing, this city of creams. It's sprung up almost overnight, like a fairy ring of toadstools, which has been my experience of the ageing process so far. It hasn't been a slow, gradual, almost imperceptible patination, like the tides working on rocks or the calciferous drip building up a stalagmite, but rather a series of sudden blows, each of which forced me to accept with a sickening lurch that I am seriously getting old.

I can remember them all quite clearly. So, in order of appearance, ladies and gentlemen, please welcome: my moments of beauty mortality.

Not being able to make my stomach flat, even by holding it in. The first grey hair. The first lines around the eyes when I laughed. The knees like caricatures of Michael Parkinson's face. The chicken wing upper arms. The suddenly loose flesh in the inner thigh (ouch! on the waxing table).

The brown spots on the backs of my hands. The permanent wrinkles around the eyes. The first varicose veins that left my legs looking like stilton cheese. The permanent forehead furrows.

The grey hairs so numerous I can no longer blow-dry my hair sleek without professional help, and even then there are antennae. The varicose veins so bad I don't want to wear skirts, even in summer. The crosshatched lines around the eyes. The crepey decolletage.

And now the latest shock - skin as dry as ancient tissue paper. This latest insult of time is the residue of a weird virus I had a couple of months ago, which delivered a horrendous facial rash, along with the usual flu-like symptoms. It is no exaggeration to say that it has ruined my skin. I have red welts across my cheeks, but those I can cover with make-up - it's the dryness that's so terrible. It's way beyond handbag, even crocodile handbag, it's more like the Mummy's Tomb. Not just dry, desiccated. Or, if you've ever seen that hilarious film She, you'll understand I'm feeling very much the way Ursula Andress looks at the end, when she doesn't get her special elixir.

So that's what I've been looking for - on the internet, the beauty pages of magazines, tips from friends - a magic potion to put a bit of mojo back into my poor starved complexion.

Are they working? Perhaps a little, but not enough.

So, vain promises from beauty jars they are. Joni was right. But as I pat and smooth and rub them in, I cling to one privilege of youth I am not yet ready to relinquish: hope.