You’re on the train, or the bus, or the tube, or the tram. Perhaps you’re on the way to work, crammed in during the damp crush of winter rush hour. Or you’re on your way home, and it’s late, and dark, and half empty. Or maybe, even, because you are young, you are on your way to or from school. Whatever the purpose of your journey, you are sharing it with other people, and, as often happens in a public place, your eyes flicker to the screen of the device of the person next to you, and that man (because it does often seem to be a man) is watching porn, right in front of you.

After BBC Woman’s Hour producer Siobhann Tighe witnessed a man doing this on a London bus, the Radio 4 programme discussed the issue at the end of last week. The response the show received over the weekend has been – aside from the predictable sadness, disgust, and outrage – that yes, this happens. Discussing it with friends and on social media, many revealed that they had witnessed it too.

I say this to pre-empt the predictable response that women so often get when they raise issues that make them feel uncomfortable, or cause them pain – whether it’s street harassment or rape – which is that what the woman has experienced is a one-off, and that feminists overstate problems like this in order to further our own agendas. In the face of such silencing women form their own networks, whether it’s in an office where all the young women roll their eyes knowingly and say, “oh, yeah, that guy”, or across a pub table with tears rolling down your face as you say to your friend: “It happened to me too.” It’s why programmes such as Woman’s Hour are so important: they provide a forum in which women can say: “This happens.”

When you see a man looking at porn in public (and yes, I know it’s not all men but a minority of them), aside from laughing, or feeling scared, or uncomfortable, you might also experience a sense of awe. Imagine, just imagine, having such a sense of ownership of and entitlement to public space that your need to watch a naked woman being penetrated outweighs the discomfort of the women (and children) in the physical environment around you catching you watching it. The lack of respect is staggering.

Some women who have shared their experiences state that the men they witnessed watching porn did so with the same impassiveness as they would view a news report. A testament to porn’s ubiquity and mundanity, perhaps. Others say the guy concerned was clearly getting off on it, in the way that your workaday flasher might by whipping out his penis.

For some, it must surely be about the shock and the upset, about feeling power over the woman watching. So much of porn sees women objectified and subjugated. When you’re in public and see a man much bigger and stronger than you looking at pornography, it’s not a huge jump to interpret his dirty smirk as “this is what you’re for. And just try doing something about it.” That was the subtext I felt, as a schoolgirl, sitting next to an old man on the bus who would alternate leering at a half-naked girl on Page 3 of the Sun with leering at me, a 13-year-old. Boys brought porn into school, too, in the form of magazines stuffed down the backs of radiators, and pictures on phones. I don’t ever recall a teacher talking to us about it, or them being told off.

Which is perhaps why there society has such a problem with porn, because these attitudes start in the classroom. Schools should do more, we are always saying this. But to do so teachers need more guidance and support. There need to be codified policies – and punishments – in place. No woman or girl should be made to feel uncomfortable in this way. No woman or girl should have to do the rapid risk-factor calculation of “do I confront, or will I get hurt?” No child – boy or girl – should have hardcore porn thrust in their line of sight when they are on their way to the Natural History Museum to see the dinosaurs.

The jury is out on whether viewing porn in public is illegal or not. Provided the person isn’t fiddling with themselves, it is not a statutory offence, though it could be outraging public decency. Either way, Transport for London has told the BBC that it encourages women to report such situations, and that the police will investigate them.

Personally, I see it as a form of harassment. Most people would say that doing it is socially unacceptable and I hope that other passengers would stand up for the person who chooses to object. It is much easier being brave and assertive when you know other people have got your back.

But it is important also to change the underlying culture, and that means starting young. Not just in the classroom, but at home as well. Too many parents are squeamish about discussing porn. They need to get over this, and start talking about it now, before watching porn becomes even more normalised.