Now this was one birthday which I hadn't been wild about celebrating in the privacy of my own home, let alone in public. On the other hand, I was itching to see what time had done to my contemporaries. Of course I wanted to know how they'd fared since leaving our windswept boarding school in Yorkshire - to hear about their jobs, children, husbands (lack of husbands). I wanted to reminisce about the seven years we spent holed up together. But, if I'm honest, what I really wanted to do was compare and contrast. After all, it's pointless to measure yourself against 40-year-olds like Michelle Pfeiffer. Instead, here would be a roomful of women all of a certain age, whose lines and grey hairs would tell me all I needed to know about my own state of preservation. In other words: was I winning?
The experience was nothing I was prepared for. The faces that greeted me as I walked into the hotel were instantly and reassuringly familiar. Perhaps some looked a little more tired than others, but on the whole everyone seemed to have weathered favourably. There were no haggard crones among us. Far more shocking was the drastic way in which a handful of women - whose clothes and hair said it all - had aged in spirit. I'm so terrified of this happening to me that I even wear trainers and combat pants when I go to the hairdresser, lest my stylist mistake me for another kind of 40-year-old, the sort who thinks kindly of curly perms. Clearly, this is a trick that one or two of my classmates don't know.
One of my clique was not only shocked by this - she bristled with indignation. "How dare they turn into frumps," she fumed. "Just because we're 40 doesn't mean we have to dress like it's all over." Indeed we don't. The next day, wearing urban black, we sat in the pub outside the school gates, nursing Guinness for old times' sake, and wondered aloud how perky teenagers could turn into WI members, seemingly overnight. No one expected Prada - but why such a premature retreat into country casuals? It was a warning. Say it together now: "We do not have to turn into our mothers."