What advice would you give to this modern moral question posed by my friend’s younger sister? A boy at school had asked her to send him a selfie. Nude, naturally. She was dithering. She liked the boy, a sixth-form crush, and was keen to endear herself. But she knew that if she sent a naked picture he’d pass it on to his friends.

She had thought of compromises: just her breasts, or her bottom coyly reflected in a mirror. It hadn’t crossed her mind to say ‘get lost’. Then, she explained, he’d tell his friends she was a prude. That, to her, was far worse than the First XI seeing her in the nuddy.

It made me glad to have been at school in the age of the Nokia, when the best a boy could hope for — and most weren’t bold enough to ask — was a tiny pixelated photo, which with good eyesight and an active imagination might just look like a naked torso.

I don’t know what my pal’s sister decided. I gave her the full treatment: ‘Just say no’, ‘your body, your rules’ and ‘love means never having to send a “belfie”[a bottom selfie]’. I said the only way to stop naked pictures being leaked, hacked and pinned to the common-room noticeboard was not to take them in the first place.

And what’s so bad about being a prude, anyway? Let’s reclaim ‘prude’. Turn it from a male insult to an empowering hashtag: #JeSuisPrude. We should be proud to be prudes. To say: no, thank you, I’d rather not.

I’m weary of having to be ‘OK’ about everything. Yeah, I’m cool with pole-dancing classes at the gym. Yeah, I’m cool with Kim Kardashian’s Brazilian wax. Yeah, I’m cool with an open relationship. Yeah, I’m cool with the picturesque, candle-lit rape scenes in Sunday night TV dramas. Yeah, I’m cool with stag-do trips to strip clubs: ‘Off you go, darling, have a lovely time.’

But I’m not cool with any of it. Nor are most of my girlfriends, all of us in our late twenties. We came of age in the naughty Noughties with sexting and YouPorn and Tinder, and we’re supposed to be super–liberal and up for anything. Some go along with it, repressing the inner prude that says: I really don’t want to do that. Then: regret, repentance, wounded pride.

I’ve seen friends abject after a break-up, not only facing the where-did-it-all-go-wrong? conversation, but also the one about whether he wouldn’t mind deleting that video and those photographs from his hard drive. Mortifying. At university fancy-dress parties the options were Sexy Witch (Halloween), Sexy Santa Girl (Christmas), Sexy Easter Bunny (Easter) and Sexy Nurse, Sexy Schoolgirl, Sexy Pop Starlet on all other occasions. You might say this was just end-of-term, Ann Summers-esque high spirits. But there is a trickle-up effect from lingerie shop to management consultancy. All female Apprentice candidates dress in Sexy Boardroom style: tight dress, clacky heels, lipgloss.

We were supposed to be the Hot Feminist generation. Our role models were Beyoncé singing ‘Single Ladies’ in a leotard and heels, and Taylor Swift celebrating female solidarity in teeny-tiny hot pants. I look forward to seeing what Millicent Fawcett wears for her new statue in Parliament Square.

There’s a telling line in the first episode of the BBC’s Fleabag, a brilliantly written, if at times appalling, series about a messed-up millennial woman played by Phoebe Waller-Bridge. Our heroine is in bed with a man who tries his luck at something previous girlfriends had refused. In a monologue to camera, Waller-Bridge says: ‘You’re drunk. He’s made the effort to come all the way here. You let him. He’s thrilled.’

You let him? When did that become the response to a man wanting something you don’t? You don’t let him do things to you. You don’t let him direct his own blue movies or dress you up like a Victoria’s Secret doll. You don’t let him bully and dictate.

Couldn’t one school PSHE lesson a term be given over to teaching girls to say: ‘No, I’m not OK with that.’ ‘No, I’m not ready for that.’ And: ‘No, what sort a girl do you think I am?’ This isn’t a plea for convent schools and no sex before marriage. Teenage crushes, first love, romance, lust, intimacy, heartbreak: I’m cool with all of that. But not with having to say yes to everything — telly rape, nudie selfies, letting him do what he wants — because to say no would make you a prude.

I say: button up your cardigans, girls. Resist the tyranny of ‘sexy’. Don’t let anyone (in the bedroom or out of it) leave you ashamed or embarrassed. Enough porno chic. Time for the revolt of the prudes.