Fiftysomething:I went to the theatre recently and saw a play about troilism. No, not the little plastic gonks with Dayglo locks and big hairy feet; troilism as in a three-way sexual encounter. Not particularly seasonal, I grant you – troilism is hardly the stuff of panto, even if it does give a whole new meaning to the phrase "look behind you".

It was an interesting evening. The first-night audience was split between friends and supporters and that other constituency, serious-looking theatregoers in vintage coats and quirky footwear, whose earnest opinions are sought and cherished.

There was a lot of laughter and the occasional hoot of recognition, and afterwards in the bar the people in the interesting shoes were doing a lot of nodding, which is always a good sign.

I was thinking about troilism on the way home – in a purely academic way, of course. It struck me that the subject matter was a far cry from the stuff of my inaugural foray into the shadowy world of theatre.

We did a play in my first year in senior school, in the convent by the sea. The play was The Scarlet Pimpernel and I was Lady Sir Percy something-or-other.

I wore a big black wig and a big sparkly pink dress from Burke’s costumiers on Dame Street. Besides getting a splinter from gliding across the wooden stage in my bottle-green knee socks, the entire process was a blast from start to finish.

There was a rhyme in the script that went: “They seek him here, they seek him there, those Frenchies seek him everywhere.”

We convent girls sniggered into our grubby cuffs every time we said Frenchies, that being the colloquial name for prophylactics in 1974, or whatever the long-ago year was.

Frenchies? The innocence! Fast-forward a few decades and here I am, sitting in a theatre listening to contemporary Irish characters playfully bemoan monogamy and the stultifying lack of sexual variety in their spanking new relationship, and I’m thinking, holy cow, it’s a far cry from rubber phalluses and three in a bed that we were reared.

I left that school in 1979, the year Pope John Paul II popped over to tell us all he loved us. To this day I remember some of the advice we received during those convent years to equip us for the big bad, gloriously dangerous world we knee-socked maidens were doomed to enter.

One simian little nun, small enough to fit in your lunch box, powerful enough to blow down a house of bricks, told us that the contraceptive pill was in fact a sugar-coated serpent, chemically designed to eat unborn babies.

A pretty intense theory. I never did figure out which chapter of the geography book she was teaching that particular lesson from.

And then there was our sociology teacher, also a nun, who doubled as our dressmaking teacher. I liked her. She had lovely brown eyes and an air of vague distraction, and I often wondered what she was thinking about while she was biting off the thread ends with her teeth.

I don’t think sociology, with its intrinsically temporal nature, was quite her bag. She once referred us, somewhat sceptically, to a chapter of the textbook that advised future wives never to remonstrate or disagree with their husbands in public.

Rather, we nubile little trainees were advised to swallow down our irritation (possibly along with a stiff Babycham) and tactfully tackle him on the subject on the way home in the car.

So that was the world our educators imagined for us, was it? A world where we girls would sit in the passenger seat, knees crossed, in our skin-coloured nylons and our home-made A-line skirt, our modest handbags full of packets of wriggling serpents, having words with our suited husbands about their indiscretions over the cheese fondue.

It was another era, a distant planet, the guidance about as useful as a punctured prophylactic.

I watch confident young girls emerge from my son’s co-educational school, strong, independent, in their jeans and their beanies, their shorts and tights, their tattered runners and wrinkled boots, graffitied bags slung over their backs, and from behind my rain-splattered windshield I feel like a time-traveller, I feel like I have emerged, only partially intact, from an ice age.

Happy New Year to them, they’ll need all the determination and resolve they can muster to navigate the years ahead. But somehow I feel optimistic, somehow I feel safe in their hands.