“The site can’t handle it,” Evans says of the online system. “It freaks out.” She adds that some customers resort to multi-screening to get their order in. Her tip is to use your phone. “It seems to be faster and with Apple Pay, you’re done.”

If the experience can be stressful for hungry customers, it is pretty fraught for Evans and Mathews, too. With four members of staff in one small kitchen, the 160-odd sandwiches they make every Wednesday, Thursday and Friday are already a stretch. And that’s before we get to Saturday’s pizza slices, for which there are no pre-orders, leading to long queues, the likes of which are more commonly seen outside Supreme stores on drop days. It’s a system that they’ve arrived at unprepared for their rapid, word-of-mouth rise rather than purpose-built to drive up sales, and Evans sounds genuinely concerned about this inconvenience for those who line up for up to 45 minutes or miss out.

To further complicate matters, sandwich fillings change every week according to supplies, season and whim. Recent highlights include the prosciutto with Napoli salami, smoke garlic, chilli pickled fennel, Sichuan pepper, mushroom XO sauce and shredded lettuce – all piled up between two slices of focaccia. And there’s always a vegan option.

“Occasionally we bring them back, when they’re really popular,” Evans says. “We get to refine them. We’ll muck around with the aioli or try a different relish or pickle. Kimchi always goes down well.”

The impact of Instagram on what we eat, and the way it looks, is well documented; TikTok, too, has caught the hoagy hype. From the scarcely believable Binley Mega Chippy buzz to the grinder sandwich craze of the past year, social media is fuelling our feeding frenzy. “Almost all of us are, on some level, addicted to those little hits of dopamine we get from likes and comments,” says dietitian, health coach and author Ms Jessica Cording. According to her, the success of the modern sandwich is not just down to the way it tastes. “These platforms have been engineered to hijack our brains that way.”

When, in the 18th century, John Montagu, 4th Earl of Sandwich, demanded meat and bread as sustenance at either his working desk or the gambling table, depending on whose account you believe, he was probably unaware that he had just invented what The Wall Street Journal would later surmise as Britain’s “biggest contribution to gastronomy”. That might have been intended as a backhanded compliment, but the events of the past couple of years have turned the statement on its head. With much of the hospitality industry closed during lockdowns, sandwiches and other takeaway edibles became an important outlet for culinary creativity, not to mention surplus produce, during the pandemic.

“Restaurants started making more complex, statement sandwiches due to Covid restricting what they could serve,” says food writer Mr Jonathan Nunn. “People got used to eating sandwiches from restaurants in their area. This trend has stuck around.”

The transition to hybrid working has allowed local bakeries to offer “a replacement for the Pret sandwich” to those who would otherwise commute, Nunn says. “I think it’s telling that 40 Maltby Street – the only sandwich in London I would probably queue for – kept their sandwich option post-pandemic, while discarding a lot of the other things they pivoted to.”

In a 2020 treaty on the art of sandwich making, Nunn decreed that “the bread must be in service to the filling”. There are signs that this new generation of bakers are taking this statement seriously. “We use focaccia because it’s fluffy, chewy, salty and soaks up sauce,” says Mr Tomek Mossakowski, social media manager at The Dusty Knuckle, which has two sites in north and east London. “If we do mackerel or ham, we might use a sourdough as it takes up less space in the sandwich.”

“We bake crusty sourdough rolls every day, most to be used for our sandwiches,” says Mr Oliver Costello, co-owner of TOAD Bakery in Camberwell. “They’re proper toothsome, chewy and rugged rolls – our preferred choice for a hunky sandwich.”

Hot on the heels of nearby Chatsworth, TOAD opened last year. And, likewise, as well as attracting snaking queues, it puts vegan options front and centre. “Our vegan offering focuses on slow cooking,” Costello says, citing tandoori-spiced chickpeas as a favourite. “We cook a lot in the residual heat of our deck ovens once the bread has been baked. It allows us to slowly braise overnight.”

The one thing London’s new sandwich kings don’t seem to be cooking up is rivalry. When asked, Costello calls Chatsworth “the real deal”; “the more the merrier” is his ethos. “Each bakery has its own USP and I’d travel for different things,” he says. “It’s the Paris model.” This echoes a sentiment Evans and Mathews voice – the dream of community-minded bakeries spread across the city like, well, relish across grilled cheese.

The rise of the sandwich is, of course, hardly unique to London. And while Britain claims to be the birthplace of the sandwich, New York is where it was perfected. The output of Katz’s Delicatessen was the stuff of legend long before reducing Ms Meg Ryan to (simulated) rapture in When Harry Met Sally…, and you can today find a sub there that’s the envy of the world on most street corners. Perhaps this is why, until relatively recently, it could be argued that the city took this lunchtime staple for granted.

“Throughout the pandemic, sandwiches have been our salvation,” Eater critic Mr Robert Sietsema wrote in a heartfelt piece in 2021. “What other satisfying meal can be wolfed down while standing up?” From confessing that he could remember “literally not having eaten one for years at a time”, Sietsema and his colleagues now regularly consider this humble one-piece meal alongside its restaurant reviews, with seasonal roundups of their standout sandwiches.

Today’s sustained buzz around baked goods is, according to psychologist Ms Shakaila Forbes-Bell, “a great example of two of Dr [Robert] Cialdini’s [six] principles of persuasion. Social proof: long queues making you think something is good because so many other people are vying to get involved – ‘Everyone else likes this sandwich so I will like it, too’. And scarcity: essentially Fomo, which occurs because humans are naturally loss averse and we think are losses loom larger than our gains – ‘I’ve missed out on this sandwich so it must taste incredible’.” We’ll have whatever they’re having, basically.

In case you were wondering, I did finally get my hands on a Chatsworth sandwich. And it did taste incredible. Was that just the collision of salt, fat, sugar and acid wrapped in focaccia or the dopamine hit of at last landing my lunch? Most likely it was all of these factors at once, some ephemeral alchemy of the right ingredients, brought together at the right time. But then, maybe that’s all a great sandwich ever is.