I watched a programme about porn on BBC iPlayer this week. I saw – and heard – things I can neither unsee nor unhear, but I’m still rather glad I saw it. In Porn Laid Bare, a group of millennials are taken to Spain where an awful lot of the stuff is made. Some of this group are against the whole business; others are very keen, er, users of this material. One lad advances the theory that “the whole world would crumble without porn”. That is quite a thing to believe. So it won’t be global warming, nuclear war or the Yellowstone supervolcano that will do for humankind. No, it will be some worldwide ban on porn, or Frankie Vaughan, as a cockney rascal I know calls it.

None of this is any kind of laughing matter if you have teenage daughters (or sons for that matter), I promise you. I dread to think what they have seen, and what conclusions they have drawn from it. I have had a carefully considered and rigorously adhered-to approach to the sex education of my children: I leave it to their mother, not least because any attempt I make to address the issue is met with horror, revulsion, embarrassment etc. I am not sure how much more success she has had.

Sample conversation in the car yesterday morning in driving rain on the way to my daughter’s GCSE history exam: “Where exactly have you learned whatever you know about sex?”

“School. Sex education.”

“No, not like that, I mean like, how you would do it?”

She shrugs. “From my friends.”

“But how do they know?

“I’m not answering any more questions about this.”

And that was the end of that.

I doubt anyone thinks porn is a good way to learn about sex, but where else do you see people, like, doing it? On what, I wonder, did I base my early efforts?

Facebook Twitter Pinterest Sex education, 80s style: Confessions of a Window Cleaner. Photograph: Everett Collection Inc/Alamy Stock Photo/Alamy Stock Photo

Not being a teenage voyeur, I hadn’t seen anyone else actually doing it in the flesh by the time I lost my virginity at a shamingly late age, so I must have been aping something I had seen on a black and white French film on BBC2. God, I hope I didn’t start trying to speak French. Also, in around 1982 when I was 15, my mate and I managed to rent Confessions of a Window Cleaner from a shop called Severn Sounds in Kidderminster. Perhaps I gleaned something from that.

All absurd, obviously, but where else was there? And where else is there now? How does anyone know what to do? Surely life has always imitated art on this – and in reference to most porn, I use the word “art” very loosely. If, in some parallel universe, either of my daughters asked me: “Pa, where can I learn to actually do sex properly?” once the defibrillator had been deployed and I regained consciousness, I still wouldn’t have a clue what to suggest. But, as my daughter did go on to say yesterday morning: “In the 1700s, they managed to work it out without looking it up on the internet, so why can’t we?”

Fair point. And on we drove, both wondering to ourselves where people got their ideas about sex from 300 years ago. I hope this didn’t cloud her mind for the exam.