A long row of sinks and at each one a woman, leaning. “They rummage through their handbags, pulling out various make-up items; applying blushers, concealers and brightly coloured lip-glosses.” In the academic book Women And Alcohol: Social Perspectives, under the titillating heading Glamour Over Consumption, this ethnographic data from a city-centre pub in Canterbury explores the way a bathroom allows women to “assess their intoxication and femininity”, taking part in a familiar form of “calculated hedonism”. Backcombing her hair, one turns to the stranger at the next mirror and asks, “I don’t look too drunk, do I?” The stranger reassures her, of course, because that’s what women do, in the toilets, at night. We urinate, we check our lipstick, and we comfort each other that we look exactly the right amount of pissed. And sometimes, perhaps knowing that otherwise we might forget this moment of uncommon warmth, we take a photo, too.

Facebook Twitter Pinterest The eminently instagrammable ladies powder room at Annabel’s restaurant in London. Photograph: James McDonald

Even when we ignore the politics of bathrooms, tiny rooms that contain our most primal anxieties and where debates about gender identity continue to play out in the media, toilets (one of the last officially gender segregated spaces in the world) are unique as sites of extreme and glittering intimacy. No wonder then, that they have also become stage sets for Instagram. A shift happened after Anna Wintour’s selfie ban at last year’s Met Gala, when the impossibility of abiding by such a frankly mad law sent celebrities trotting with their phones to the bathroom. The resulting photos – from Kylie Jenner’s Last Supper-like selfie, featuring a menu of stars including Frank Ocean and Brie Larson pouting in the mirror, to those of models smoking louchely on the tiled floor, one shot captioned ‘Real VIP Room’– inspired an art exhibition in Brooklyn, where visitors received candy cigarettes on entry. Elsewhere, toilet selfies are going viral for different reasons. When Twitter user Paula Sophia Garcia Epsino posted a photo sitting on her aunt’s bathroom counter in Mexico, the internet paused to marvel, briefly, not at her tiny shorts, but at the boggling placing of a toilet roll holder across the room from the toilet. Each person imagined their inevitable waddle.

Facebook Twitter Pinterest Leanne Young used the time she was stuck in the loos at Isabel in Mayfair productively. Photograph: @leanneelliottyoung/Instagram

It was a Tuesday night, and Leanne Elliott Young, a creative director based between London and New York, was stuck in the loo at Isabel, a new Mayfair restaurant where each toilet features a unique hand-painted wallpaper of tropical flamingoes or Korean peonies. She used the time to read the graffiti on her Ingrid Kraftchenko boots (“They’re not just shoes,” Young insists, “they are deep with sorrow, dramatic aggression, contemplations and conversations with the self”) and enjoy the drama of her Charles Jeffrey flag dress, after “decoding the visual syntax and semantics of this flag by @_charlesjeffrey”. The fancy bathroom, with its marble ledge and big mirror, was ideal. “Where else can you get your foot that close to your face?”

Facebook Twitter Pinterest Kylie Jenner and friends in ‘the real VIP room’ at the Meta Gala. Photograph: KylieJenner/Instagram

The distant toilet roll holder is not a mistake many interior designers will make in future, having learned (through the millions of likes under hashtags such as Young’s) the importance of an Instagrammable bathroom, including the obligatory marble ledge. To scroll through bathroom selfies is to rinse yourself in orchids and the colour pink, with women selfie-ing themselves in poses they’d be shy to make in public. Or, after two or three drinks, with their friends. Or, after three or four, with strangers. Makeup artist Charlotte Tilbury, creator of “glow”, was hired to ensure the bathroom at London club Annabel’s, with its flowered ceiling and vaginal colour palette, was the optimal space for applying, then documenting, your makeup. She added lighting dials, for guests to perfect their reflection, and it worked – after washing their hands, women gather nightly, hand on hip, in a space built for photographs as much as hygiene. While bathrooms have always been the places where we bond and lounge and rebuild ourselves with new layers of bronzer, now they are being designed with the performance of femininity in mind. There are the girly pink powder rooms, the monochrome cells with tiles that tessellate oddly when drunk, like Ibérica in Leeds, the womby boudoirs, the maximalist jungles with erotic wallpapers and more pillows than a hospital, and the mind-bending halls of mirrors, such as the bathroom at Yotam Ottolenghi’s Nopi in London or Crazy Bear in Beaconsfield, where a single selfie goes on for miles.

Facebook Twitter Pinterest The mind bending mirrors that ricochet selfies for miles at Crazy Bear. Photograph: Paul Wilkinson/The Crazy Bear

Young is a queen of the bathroom selfie (for her money, the top three are all in London: the Ritz, Sketch and Hoi Polloi), in part because of her sense of toilet humour. But she says the rise of the selfie has changed the bathroom experience. “Now it’s a place of cold blank pouty stares into the void of social media likes. Taking photos, most people forget to wash their hands. And you get to see the ugly side of a selfie. That blue steel pre-filter, pre-Facetune duck face. The idea of pouting semi-naked, somewhere you’ve just evacuated your bowels, still makes me laugh out loud.” Though she delights in sharing her own bathroom selfies, along with, at last Instagram count, 1.4 million others, it’s getting more difficult. “The queues were once miles long due to folk snorting coke; now it’s because they’re tussling around to get the best shot. I’m in and out quite quick, toilet seat up, toilet rolls in full view, snap!”

Which is not to say she hasn’t considered the place of the bathroom selfie in popular culture, compiling her own casual ethnographic data. “It’s a moment that blurs the private and public. It’s a public place that you’re private within.” There’s a lock on the door, “so it’s a private space to curate. To be scantily clad but snapping away. To be free!”

Around Eva’s sink are her makeup recommendations for an Instagrammable night out (from left): Wonderglow, £38.50, Charlotte Tilbury. Eleventh Hour hair perfume, £48, Byredo. Bronzer, £35, Lilah B. Brush, £19.99, Zoeva. Glitter Balm, £13, Winky Lux. Brush, £9, Zoeva. Eye Polish, £26, RMS Beauty. 20 Year Anniversary Eye Shadow Palette, £76, Chantecaille. Hydrating Long Lasting Lipstick, £38, Sisley. Cloud Paint, £15, Glossier. Killawatt Freestyle Highlighter Duo, £26, Fenty Beauty. Styling Melanie Wilkinson, photography Louisa Parry.