I celebrated my 50th this year. Well, I didn't actually

FIFTYSOMETHING:CELEBRATED MY 50th birthday this year. Well, I didn't actually, not like I planned. When it came down to it, I just cycled over to my mate's house and drank the contents of her fridge, avoiding anything in a carton for fear of contaminating my alcohol with vitamins.

I had great plans, of course: in the sanguine recess of pre-50 musing, I’d imagined a shadowy room with a balcony and a gin fountain, and me blowing smoke rings into the rakish faces of my dashing friends. I don’t know why I thought being 50 would catapult me into a sultry maturity, I don’t know why I thought I’d wake up gracious and wry and suddenly and inexplicably willowy (nil by mouth and a year on a rack wouldn’t help me achieve that last adjective).

A couple of months into my new decade, and my imagined 50-year-old self continues to elude me. Where is she, the sleek sophisticate with the knowing laughter and the awfully good teeth, and who is this groggy imposter with the undulating thighs that I wake up inside every morning?

I glimpse her occasionally in the rear-view mirror, this older woman I’d supposed I would morph into; I catch sight of her out of the corner of my eye, this me I am not.

There she is, stepping into a taxi in nude high heels or unbelting her mackintosh in a revolving door; she’s sinewy and vegan and spends a lot of time in duty-free, rubbing elixirs into the feathery lines around her eloquent eyes; she’s a marine biologist or an art dealer or an organisational analyst. She certainly doesn’t take used razors out of the pedal bin.

I think that, growing up, I had a problem with role models. Who were they? Plaster saints with plaster babies at their well-wrapped bosom? Dusty Springfield in false eyelashes? Nuns in tea towels? I think somewhere along the line I missed the point about role models: I couldn’t have named a single female scientist or explorer or painter, although I did admire the way Angie Dickenson looked in a trenchcoat.

“Who do you think you are?” our mothers used to hiss at us when we were slipping out the front door with 10 fags hidden in our pencil case and our school skirts rolled around our midriff. Good question, mother. Half a century into this game and I still haven’t found the answer.

I suppose I thought I’d grow up. I suppose I thought I’d wake up one morning with a wardrobe full of slingbacks, and they’d walk me into adulthood.

When we were 10, my class was gifted with an extraordinary teacher. She was English, she wore a red polka-dot dress, she smiled at us. She stood before us on that pale September morning, a class full of little girls in too-big-for-us grey tunics and buttoned-up cardigans, and told us that we were going to do a project. It was the first time I’d ever heard the word.

We were to write our autobiographies. I was so excited I had to remind myself to breathe. In that sombre convent school, where we were warned never to start a sentence with the word “I”, writing an autobiography was a heroic, subversive task.

I found mine the other day. Some now-I’m-50-I’ll-clean- under-the-bed gene kicked in, and there it was, a foolscap copy, my autobiography, each chapter heading underlined. Food Fads. Private Thoughts. My Family.

My Friends. What I Think Is Wonderful. Me When I Am Older. A drawing of Me When I Am Older (one I suspect I may have been awfully proud of) depicts an anxious-looking woman with what may or may not have been a brace of sausage rolls on top of her head, waving her arms around opposite a moustachioed man in a doublet and hose; in another picture, she is in a wood with an easel, painting trees.

“I have blue eyes that are deep and fathomless, I think God is wonderful, and when I grow up I will live in Switzerland.” I think it’s time to go back to the drawing board.

Who do we think we are? When do we ever find out? Apparently, women of a certain age, my certain age, are the bane of marketing executives’ lives. They don’t know how to sell to us, they don’t know what we want, they can’t categorise us. We don’t want their nappies or their breast pumps any more; we don’t want their alcopops or their bubblegum-flavoured prophylactics; and we’re not yet in the market for their stair-lifts.

Who do we think we are, we rumpled daughters of Eve? Answers in your foolscap copies – and lengthen that hem on your tunic.