They say you can tell if an Italian restaurant is any good based on whether or not Italians eat there. The man behind me was from Naples.

“It’s simply the best sandwich you’ll ever have in your life,” he enthused. “The bread reminds me of my nonna’s, when I was a child.”

We were in the queue outside All’Antico Vinaio, a sandwich shop that first opened its doors in Florence in 1991 and became a sensation across Italy, opening outposts in Naples, Bergamo, Bologna, Verona, Milan and Rome, before taking its creations to Dubai and America. By 2014, it was the most-reviewed restaurant on Tripadvisor of all time.

Our queue was outside its new London branch in Soho which – thanks to the social media buzz – had snaked round the corner and involved a 45-minute wait, overseen by a security guard that polices the crowds after a neighbouring restaurant complained about the queue preventing access to their customers.

Our goal? To order one of All’Antico Vinaio’s giant sandwiches (for which the Neapolitan was on a return visit) which are assembled between schiacciata, a Florentine flatbread similar to focaccia but thinner and crispier, piled high with speciality Italian meats and cheeses including smoked provola, pecorino, stracciatella and buffalo mozzarella.

Long queue at sandwich shop, All'Antico Vinaio, based in Soho

So long have the queues been that All’Antico Vinaio have employed a security guard to organise the hungry crowds – Heathcliff O’Malley

Their prices are similarly lofty: a sandwich bearing just two ingredients (mortadella and stracciatella, say, or prosciutto crudo and pecorino) costs £9.90, while the top-tier signature sarnies go all the way up to £14.90.

Pret A Manger’s £5.99 baguettes look ridiculously good value by comparison. How can a £15 sandwich ever possibly be worth it?

As I neared the front of the queue I discovered the reason for its slow progress. Four sandwich makers were painstakingly carving slices of ham, chopping up fresh juicy tomatoes and cutting apart plump balls of mozzarella. Pre-prepared, Subway-style sandwich fillers these clearly were not.

Food counter inside of All'Antico Vinaio, a sandwich shop in Soho

In contrast to many chain sandwich shops, the ingredients are prepared to order at All’Antico Vinaio – Heathcliff O’Malley

The creation for which the chain is most celebrated is the “Bada Come la Fuma” (mine, eventually, for £14.90). Filled with porchetta, smoked provola cheese, potato cream and spiced aubergines, the bread sprinkled with fresh olive oil to soften it, this was a big sandwich – easily 15cm by 15cm, as thick as three folded copies of The Sunday Telegraph. Not for the first time while assessing a viral food phenomenon, I felt it was a shame I couldn’t actually disconnect my jaws, anaconda-like, to swallow such food the size of my head. C’est la vie.

Having to settle for an undignified chomp, which sent wads of provola and porchetta tumbling down my front, I masticated manfully through the hefty wedge of sandwich. Suffice to say this is not a work lunch for those looking for a quick snack between meetings. A bib is advisable.

I was disappointed to find my sandwich rather cold, not least because “Bada Come la Fuma” translates as “Look how it smokes”, and has become the sandwich chain’s slogan after owner Tommaso Mazzanti made numerous videos of opening up the warm bread showing steam rising from it.

Sandwich from All'Antico Vinaio containing meat and cheese

The sizeable sandwich contained provola cheese, porchetta and aubergines – Heathcliff O’Malley

Due to All’Antico Vinaio’s status as a small operation in the UK, it doesn’t currently have to print calorie counts on its menu, but what with the tapestry of riches within, and the sheer size of the sandwich, I’d be stunned if it wasn’t at least 1,500kcal.

But I can’t deny the quality and flavour – the delicate smokiness of the provola cheese, the moreish meatiness of the porchetta and the gentle spice from the aubergines was a delicious blend. Genuinely, mouthwatering stuff.

The price is extortionate – I can remember when a sandwich passing the £10 threshold was considered reputational suicide – but given I only managed about a third of it in one sitting, it can stretch to a few meals. If, that is, you don’t mind an onslaught of roast meat and smoked cheese at each sitting.

This viral sandwich might be a cut above but the idea of parting with £15 for it is mind-boggling, and not something I’ll make a habit of. Tomorrow, I’ll be back to my supermarket meal deal.

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Dining and Cooking