When I was a university fresher, my friends and I invented a fourth meal of the day. We christened it 'pstub' – a contraction of 'post-pub', though it also sounded a little like 'p***ed-up', the main circumstance under which it was eaten.

Pstub began in a casual manner; falafel wraps from Woody Grill on Camden Road, which would dribble garlic sauce down your best going-out dress. Slabs of baked cheesecake from Brick Lane's Café 1001, delicious for the novelty of being able to eat them on a dancefloor. Cheesy chips from Dionysus (RIP), the ghost of which now haunts the Tottenham Court Road Crossrail platforms. Great heaps of fish fingers and ketchup, served family-style straight from the baking tray. Fray Bentos tinned pies, beloved for their novelty ("It's a pie! In a tin!") if not for their greyish innards.

But soon, things gathered pace. Pstub grew more elaborate, and the food began to overshadow the parties. We'd be dancing in some basement bar or other, checking watches, already plotting the roast chicken or pad thai we were going to rustle up when we got home. Oneupmanship ensued, as we tried to out-pstub one another. There was even a Facebook group, 'The Pstub Revolution Cometh', because this was 2006 and no activity or quirk was allowed to go unsanctioned by the big blue thumb.

Pstub had rules. It had to be eaten after midnight in order to qualify, and the closer it was to dawn, the more bountiful the feast permitted. Calories don't count at night, as we all know, so it was free from nutritional concerns. But the most important criteria was reverence. This was a proper meal and had to be treated as such. Never mind that it was eaten at 3am under a strip light in a university halls kitchen last refurbed before decimal currency; every pstub was an occasion.

Now, my clubbing days have long since passed, but the fourth meal of the day lives on. In fact it's a bona fide trend, as anyone who has ever felt cheated out of a meal by brunch will be glad to know. "There is growing evidence that we are starting to squeeze a small, fourth meal into our daily routine," claimed last year's Waitrose Food & Drink Report. "This is not about gluttony; rather about adapting our eating schedules to our busy lives." (Though the 21,459 #fourthmeal posts on Instagram, a hedonic parade of pre-lunch toasties, post-gym burgers and midnight pizzas, might beg to differ.)

The British afternoon tea seems to have jumped the shark over the past few decades

The reason we stick to a schedule of three meals a day is largely cultural, neatly bookending a typical 9-5 work day. It's not biological instinct, nor set in dietetic stone. And while the idea that eating 'little and often' can raise the metabolism has now been widely debunked (sorry), the elusive fourth meal is more than just hyped-up snacking. It's about pleasure, ritual, escaping the demands of the day for half an hour. Mindfulness, even. If a fourth meal has a health benefit, it's giving us permission to take a proper break, with something more exciting than a KitKat to keep the wolf from the door.

Afternoon tea could be said to be Britain's fourth meal, but it seems to have jumped the shark over the past few decades. Once a daily custom, it's morphed into something the average person might do once or twice a year, and despite the prevalence of restaurants and hotels offering either traditional or 'alternative' afternoon teas, in actual fact it seems more the preserve of hen weekends, Mother's Day outings and Groupon vouchers for underbooked spa hotels. Instead of the humble greediness of an Enid Blyton-style prefect's tea, all anchovy toast and marmalade by the fire, these days we must fork out twice the price of a two-course lunch to be served crustless bread and tiny tarts like an aristocratic toddler. Elevenses, meanwhile, has done rather the opposite: deprioritised and villainised as we all strive to optimise both our bodies and our working day. Stopping for cocoa and buns in the middle of the morning? You need a better slow-release breakfast, mate.

Personally, I don't think four meals a day is particularly extravagant. Hobbits, you might remember, eat six – including a second breakfast, and a second dinner if they can get it. Fiction is full of these meals-between-meals; the "little smackerel of something", plot twists helped along by piles of hot buttered toast and mugs of good strong tea. We might think of the dripping crumpets and gingerbread in Daphne Du Maurier's Rebecca, or equally lavish afternoon spreads in Henry James and Agatha Christie. Or we could look to those notable Londoners, Paddington Bear and Mr Gruber, who favoured hot cocoa and buns for their daily elevenses.

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Of course Paddington and Mr Gruber, we might note, were both immigrants who made London their home and created new pockets of familiarity within it. While Britain might have the monopoly on scones and cucumber sandwiches, almost every culture has its own bonus mealtime – a way to break up the day that's equal parts social and satiating. And despite claims that we're adopting the 'New York day', getting up earlier in order to squeeze in an extra spurt of productivity before work begins, maybe we'd fare better taking a few tips from our European cousins.

In Valencia, almuerzo is a vital second breakfast – anything from a small pastry to a heaving ham and cheese bocadillo – eaten around 11am to see you through to a languid lunch. A Pret baguette might not hit the same spot, but José Pizarro's mini serranito sandwich, stuffed with Ibérico loin, jamón, toasted red pepper and manchego, can be scarfed from 11.30am at his Broadgate Circle outpost. You're welcome.

Croatia has a similar tradition, mainly upheld by older generations, of a sociable mid-morning stopgap. In the tavernas of Split this is a meaty, spoonable affair – sometimes stewed beef, braised cuttlefish or even tripe – but more widely, marenda will be a platter of charcuterie and cheeses, perhaps an aged sheep's milk offering like the brightly tangy paški sir, from the island of Pag, alongside rounds of spicy kulen sausage and glossy ribbons of prosciutto, slow-cured in the cold Adriatic winds. Croatian culture is characterised by "an obsession with food," says Chris Stewart, who opened Borough Market's Taste Croatia deli nine years ago. "You plan lunch, you talk about lunch, then during lunch you'll talk about what you're going to have for dinner." Hardly surprising, then, that time can always be found for an extra sit-down over coffee, both before and after work – a leisurely attitude that Stewart believes Londoners would do well to copy. "They don't have the concept of takeaway cups in Croatia," he grins.

Once that lunch is out of the way, mid-afternoon is prime time to squeeze in a mini-meal. Popular legend suggests that the French don't snack, and yet the after-school goûter, also known as le quatre heures (the 4pm), is a basic right. Pain au chocolat; a baguette spread lavishly with Nutella; a stack of frilled Petit Ecolier biscuits – your reward for a school day completed, or a work day three-quarters endured.

Then of course there's fika, Scandinavia's sainted coffee and cake break, which arrived on these shores around the same time hygge did but has demonstrably better staying power (there are only so many scented candles and cashmere socks a person needs in their life, while enriched dough is a limitless commodity). "Fika is both a noun and a verb. You can fika with someone, or you can have a fika with someone," explains Brontë Aurell, author and co-owner of Fitzrovia's ScandiKitchen. "But you can't fika alone, it is a social thing. It's taking time out to sit, connect, eat, drink and then go back to what you're doing."

There are only so many scented candles and cashmere socks a person needs, while enriched dough is a limitless commodity

While we might know it as a mid-afternoon treat, you can fika in the morning too. You can fika with colleagues, with friends, with family, outside, at home, even on a date. But the one place you cannot fika, and on this Brontë is firm, is al-desko.

"The purpose of fika is not the coffee or the bun itself, but the act of breaking from what you're doing," she says. "At work, you leave your desk and you go to the break room for a fika break. At home, you sit and talk around the table or coffee table." Unsurprisingly, phones are another no-no. Scrolling while you sup just won't cut it.

The classic fika snack is the cinnamon bun, these days to be found wafting seductively from bakeries and markets all over town. Every Scandophile in the city has their favourite, be it the cardamom-spiked, sugar-crusted kanelbullar at Bageriet in Covent Garden, the dense, buttery knots at Fabrique, or the burnished scrolls the size of your head at Nordic Bakery. ScandiKitchen's own signature bun is gooey-middled, chubby and golden with a liberal sprinkling of sugar pearls. Listen very carefully during their 'buy bun get bun free' promotion every Wednesday morning, and you can hear Fitzrovia buzzing.

But while the sweet treats give it marketable appeal, it's coffee that's the real cornerstone of fika. Norway, Denmark and Sweden are among the biggest coffee consumers in the world, with an artisanal fervour to give the Antipodeans a run for their money. And when you're serious about drinking a quality cup, you'll take the time out to make it. The simple ceremony of brewing a stovetop pot of espresso, waiting to plunge a cafetiere or taking a walk to the nearest barista offers a chance for a mental stock-take, in a way that rehydrating a sad teaspoon of Kenco never will.

"We see many people who pop by mid-morning and again mid-afternoon for fika – and not just Scandinavians," Aurell tells me.

"I think Londoners were looking for an excuse to take more breaks; to leave their desks and go outside for a few minutes of fresh air and a cup of tea or coffee. We work so hard here, and such long hours. I think people were yearning for something that meant [taking a break] would be okay."

I've been one of those Londoners, hitting the 3pm slump and 'treating myself' to a few minutes away from a screen to answer the siren call of zone one's warm ovens. It's a sacred expedition. The perk-me-up power of a flat white and a sugar fix cannot be oversold, but it's as much about the opportunity to unfurl your spine, stretch your legs and do a little light bitching with a colleague in the sanctity of a quiet side street. Fika might be highly caffeinated, but it forces you to slow down, too.

Once work is over, of course, there's another prime pocket of time in which to tuck an extra meal. Aperitivo hour, the snacky, pre-dinner buffet served alongside a bitter aperitif, is an Italian institution that has been gathering fans in the capital since the summer the Aperol Spritz went viral (2014, in case your memories are hazy).

"More and more people are starting to embrace the aperitivo. It's definitely something we're going to see in the cities – London, Manchester, Liverpool," predicts Natalia Ribbe, co-founder of Ladies of Restaurants, who hosted her own aperitivo hour at this year's Taste of London festival. While a typical 5pm tipple is usually heady and herbaceous – Aperol, negroni, Campari, vermouth – the accompanying spread should be simple, but more than just a salty soaker-upper. "Some lovely olives, some great charcuterie, a little bit of cheese and a nice cocktail. Nothing overcomplicated. Nothing with umbrellas," she says.

The beauty of the aperitivo hour is that it's the epitome of relaxation

London's dinnertime has been creeping forward with the rise of the no-booking policy ("If I bunk my final meeting and leap straight on the central line I can be there by 5.45pm to guard the table!") and the quest to snag the most talked-about table has begun to feel like work in itself. On a balmy summer evening, wouldn't we rather be sitting and sipping at a pavement table than queuing round the block for yet another Insta-famous taco? Could aperitivo be the more civilised answer?

Ribbe thinks so. "The beauty of the aperitivo hour is that it's the epitome of relaxation. It's that time at the end of the day, before your next social engagement, where you can unwind," she says. After all, aperitivo means 'to open'; be that loosening a tie, spilling some juicy gossip or just declaring the weekend begun. "I think if we can learn anything from our European friends it's about loving that moment, switching off and really just enjoying it."

Beyond Italy, she's found endless spins on the post-work bite. "In Barcelona, deep-fried thick-cut potato chips, beautiful boquerones, spicy peppers… in Vienna, everyone meets down the Naschmarkt Urbanek and they do these amazing Austrian cured meats with freshly shaved horseradish and German-Austrian mustard." Yet here, in a country where drinking can be a standalone activity in its own right, we're late to the party when it comes to appreciating all the ways food and alcohol can work in delicious harmony. Eating, let's be clear, is definitely not cheating.

You can find first-rate aperitivo at London's finest Italian drinking dens; Soho's Bar Termini, where Tony Conigliaro's cocktails are mopped up by paninis, burrata and beef carpaccio, Chelsea's glittering Ritorno, where the lavish happy hour lasts from 4-9pm on Sundays, and for the veggies, Bethnal Green's Hive of Vyner Street, where hummus, activated almonds and buffalo cauliflower are all on the menu. But the traditional happy hour buffet, where punters pay for drinks but graze for free, is still hard to come by in the capital.

The next best thing might be Covent Garden's Italian farm deli Rosetta, where £25 will get you two cocktails and a sharing platter groaning with cheeses, charcuterie, grilled vegetables and olives. Manager Luciano Russo tells me that they enjoy introducing rookies to the art of aperitivo, though it's still largely Italians pulling up a chair come 5pm each day. "Italians create their own little Italy wherever they go," he says. And true to the legend of the fourth meal, it's as much about the people as the provisions. "You go, you meet people at the bar, you chat, you socialise, you make new friends." Is a solo aperitivo acceptable? "No! Never alone."

A bagel from Beigel Bake in Brick Lane, London

The bagels at the 24-hour Beigel Bake in Brick Lane are a familiar fourth meal to many Londoners

Of course, what we might call aperitivo, your mother might call 'spoiling your dinner'. But then that's a perfect excuse for the most deserving fourth meal of all: the midnight feast. Whether that's a Nigella-style fridge rummage in your most formal dressing gown, or eking out a night out that you don't want to end quite yet.

Until recently, London was less the city that never sleeps, more the city that naps against the night bus window. But now, bolstered by the night tube, our late-night dining options are expanding beyond caffs and kebab houses. Duck & Waffle is famously open 24 hours, and that eponymous signature dish will sharpen you up enough to enjoy those twinkling views and make up for any crowds of braying bankers. Smoking Goat Shoreditch serves its volcanic nose-to-tail Thai until 1am (duck laab for the cab, anyone?), while at Chinatown's chaotic Lanzhou Noodle Bar, the knife-cut dao xiao mian pull in the crowds until 2am on weeknights and 5am on weekends. And of course, there's no better way to greet the sunrise than with a Brick Lane bagel in hand, oozing mustard and fat chunks of salt beef – a personal pstub favourite, all those years ago.

But whatever you call it, wherever you find inspiration and whenever you decide to squeeze in a fourth meal, it deserves proper attention. Sit down. Eat slowly. And above all else, make it an occasion. Though if you find yourself starting a Facebook group, it's possible you've gone too far…