Pizza Pilgrims brothers head to Italy on the hunt for the very best lemons for their new Sohocello

James and Thom Elliot plan to buy a ton and a half of Amalfi lemons and ship them to the UK to make their own good-quality limoncello

Luigi Aceto's lemons are grown on the terraces of his grove on the Amalfi coast (Sam Wrench)

A 6am flight, the dusty concrete-rama of Naples airport, a sweaty journey through snarls of motorway traffic, a quick stop at our hotel, and we're sat at a long table crowded with a dozen pizzas with the circumference of beach balls, and icy glass bottles of Coca-Cola.

There are 13 of us in the upstairs room of Pizzeria Trianon di Ciro. Sun and the sound of traffic streams through the open windows. The pizzas have been ordered from laminated menus by James and Thom Elliot. They know their stuff. Two years ago, the two brothers quit their respective jobs in film production and advertising to set up Pizza Pilgrims in Soho which, arguably, serves London's most authentic Neapolitan pizzas.

There is a pair of margheritas. A white pizza, made with cream instead of tomato, topped off with fennel-spiked sausage and broccoli. Another with funghi, tinned and delicately soft and delicious for it. And, best of all, a pizza marinara: the base covered with a garlicky tomato sauce, dried oregano and puddles and rivulets of peppery olive oil that runs down your fingers and makes your mouth hum.

"Leoparding," says Thom, folding over a pizza and pointing to the charred black spots on its base. "You want the oven to be so hot that certain parts of the dough take on colour. It shows the dough is fresh and handmade – you'd never get it with packet yeast. If you left it in for another minute, it would be burnt."

James and Thom started selling pizza first from a Piaggio van fitted with a wood-burning oven in 2012, and then from their Soho restaurant a year later, based on findings from a research trip around Italy. They're back with a plan to buy a ton and a half of Amalfi lemons and ship them to the UK to make their own limoncello.

They believe there's a gap in the UK market for a good-quality version of the traditional digestif. Most of what's served here is made from powdered lemons. By importing some of the world's finest citrus fruits and taking them to the Chase Distillery in Herefordshire, they hope to make a top-notch, authentic alternative – by way of the English countryside. Ruddy-cheeked and affable, it's hard to doubt their infectious optimism. "I guess we have this slightly naïve attitude to things," Thom admits. "Like 'Ah, how hard can it be to do this?'. It's actually quite good because once you're in it, you might as well do it all."

The plan is to set off the next morning and drive 70km – past the foot of Vesuvius and the ruins of Pompeii through twisting mountain roads – to the Amalfi coast. But the rest of today is to be spent sampling the best of Naples' food.

After a walk through the faded Plebiscito Square, we arrive at an osteria, the Friggitoria Presidente. Pig trotters and tripe hang from metal hooks alongside vines of the local lemons. They're large and nobbly and look magnificently fresh. In comparison, their cousins found in British supermarkets (usually from North Africa) look like garish cricket balls. "This was such a treat as a child," says our translator Eddie as he orders excitedly in Italian.

We are served two plastic plates of the trotters, boiled to the palest pink and split length-wise, revealing an intricate cross-section of bone and sinew, like an anatomical model. Before handing them to us from behind his metal counter, a man in dirty white overalls slices open a lemon and squeezes it over the top with a crunch of sea salt.

The team drove 70km – past the foot of Vesuvius and the ruins of Pompeii through twisting mountain roads – to the Amalfi coast (Sam Wrench)

Standing on the hot, dusty pavement, as scooters whizz by, we tuck in. In terms of texture, it is like biting through a pencil eraser. The flesh is cold and peels from the bone. While Eddie gnaws through one trotter and then a second, the rest of us find it hard to stomach. But the explosive zing of the lemon juice is unmistakable – complex and aromatic, it cuts through the fat and almost makes the dish palatable.

Next, it's stracciatella ice-cream and sfogliatella riccia (thin-leafed pastries shaped like lobster tails filled with sweet cream) before a dozen more pizzas at Di Matteo for dinner. On the walk home through the winding streets, overhung by balconies and hanging laundry, we stop at a hole-in-the-wall for the city's other speciality: deep-fried street food. We eat arancini piccolo, frittatina, melanzane, and polpo, all crisply battered and salted and costing a few cents. Before finally, yet more pizza: a deep-fried calzone; surprisingly light, filled with tomato and basil leaves and sweet, creamy ricotta.

Limoncello, says James, is very similar to pizza. "It's simple," he says. "There are four ingredients, but it's all about the quality. Everything has to be there. If you haven't got the right lemons and spirits, it's always going to taste bad."

James and Thom Elliot and the Pizza Pilgrims team sourcing Luigi Aceto's lemons in Amalfi for their Sohocello drink (Sam Wrench)

With your ingredients sourced, the first step is to peel the lemons and steep the rind in alcohol for three weeks. Then, boil together water and sugar and add to the alcohol. If you have used good-quality ingredients, the liqueur will emulsify, turning cloudy. This is known as the louche effect and is caused by the oil in the lemon peel emulsifying with the water.

Luigi Aceto believes his Amalfi lemons are the best. They are grown on the terraces of his grove which curls around the side of a hill overlooking the sea. He's been offered a lot of money for the land by property developers but he says he will never sell. He is a sixth-generation lemon grower and he still does things the way his papa and nonno did. Instead of wire, the lemon vines are bound to their growing frames with boiled willow twigs. With pride, he demonstrates his one concession to the modern world: a rusting metal crate on an electronic pulley system which can carry two boxes of lemons at a time down to the foot of the grove. "He wants to be traditional and organic," explains his son Marco, who also works on the grove.

Leading us along a winding path up the terraces, he carries a ladder which he occasionally places against the dry-stone wall to climb and hack a lemon from a tree. The breeze smells sweet, of citrus and earth and sea salt. Mint and fennel grow on the path along which we walk. Crushed under feet, the plants add their fragrance to the mix. It is this heady breeze, which brings light relief from the spring heat, to which Luigi says Amalfi lemons owe their superior quality. "The draft blows through the valleys and makes a microclimate which is unique," he says. "It is the same breeze that dries the local pasta."

James Elliot samples some local limoncello (Sam Wrench)

Twisting one of the lemons in your hands is enough to make the all-important oils burst from the pores in its skin. Unlike the rock-hard fruit Brits are used to, the rinds are so soft they can be peeled by thumb, like a tangerine, and the flesh is sweeter and can be eaten – albeit in cautious mouthfuls.

Asked why he grows lemons and not one of the other local crops, such as oranges or olives, Luigi becomes teary-eyed. "I love lemons so much I almost want to cry," he says. "I was conceived in a lemon grove – all of my seven brothers and sisters were – and I grew up in a lemon grove." Pointing to a cut on his head, he says that when he bashed his forehead earlier in the day, he quickly plucked a lemon from a tree and squeezed the whole thing over the wound. Those who know him call him 'papa limon'.

Reaching the top of the grove, Luigi shows us a single room with a view out to sea. He rents it out occasionally, he says, "but only to poets and lovers". We sit outside it in the dappled shade of the trees as numbers are discussed. A deal is soon struck and we head back down the dirt path under the beating midday sun in search of lunch.

Back in London earlier this month, James and Thom call to say the first sample bottles have arrived. Over perfectly leoparded pizzas – one with sausage as tasty as any we had in Italy, another with fresh Portobello mushrooms, and a third with aubergine – they fill me in on their lemons' return journey.

The finished product - Pizza Pilgrims' Sohocello limoncello (Myles New)

As planned, all 8,000-9,000 of them had arrived in Hereford two weeks later. Mr Aceto had shipped them before they had had time to make payment. Peeling this many lemons is no easy task. James and Thom gathered up staff and friends and put out a tweet. Before long, they had 22 people in a mini bus, heading for Hereford, where, aided by copious gin and tonics, they spent six hours peeling.

After lunch, James brings out one of the very first bottles of Sohocello. The frosted glass shimmers and the muted yellow liquor inside is satisfactorily murky. He pours three glasses. Colder than ice, the drink explodes in the mouth: the aromatics of the citrus, cut through with the clarifying astringency of the alcohol. To get the most out of their prize lemons, James and Thom reduced the sugar and alcohol content, pushing the fruit to centre stage. "You can still taste lemon five minutes after you've finished drinking it," Thom points out. "That's the oil content."

And so it is that heading back to the Tube, through scaffolding and roadworks and over rain-soaked pavements, my mouth hums with the taste of Mr Aceto's lemons.

EasyJet flies to Naples from five UK airports (Bristol, Edinburgh, Liverpool, Gatwick and Stansted), with flights starting from £23.74 per person (one-way, including taxes and based on two people on the same booking). All flights can be booked at easyjet.com.

Sohocello will be available at a handful of retailers, including Gerry's Wines & Spirits in Old Compton Street, Soho, as well as at Pizza Pilgrims in Dean Street for £25 per 50cl bottle