PHILIP ERATH SHAKES his head and looks blank. "Gosh. That's a really difficult question. I'm not sure I've ever been asked that." Erath, who runs Notting Hill's pioneering Spice Shop, repeats the question to his wife, Yaziz, knee-deep in delivery boxes downstairs – while I fight the temptation to crow delightedly. After over half an hour of plumbing the couple's exhaustive knowledge of spice's history and uses, I've finally stumped them with a simple question: what do you think of as spice?

What does anyone think? The Oxford English Dictionary defines spice as 'an aromatic or pungent vegetable substance used to flavour food', which is a good starting point. It rules out salt, at least – and while the OED doesn't cover it, those in the industry have conclusively ruled out herbs. If it's the leaf of the plant, then it's a herb; if it's anything else – roots, seeds, bark and fruit – then it belongs in the spice rack. But such clinical clarifications don't scratch the surface of humanity's long and impassioned relationship with spice, and its use in food and drink.

Take London, for instance: a cultural and culinary melting pot that for centuries has been routinely sprinkled with spices. The birthplace of the East India Trading company in the 19th century – and the beneficiary of bounty from the Crusades and other Imperialistic endeavours in the East before that – it has long been familiar with the spices and seasonings of that part of the world.

In fact, so assimilated are nutmeg, cinnamon and mixed spice in British food that Magali Russell, owner of the Spice Mountain stall at Borough market, cites stories of tourists coming to her stall looking for these 'British spices' to take home as souvenirs. "They look bemused when I tell them they're not from here," she laughs, "though they are in all the old British recipes. Generally speaking, in Europe and North America – where spices don't really grow – they have adapted spices grown elsewhere to their own cuisines."

Coriander seed, used in korma in India, has long been used as a pickling spice in Scandinavia; turmeric, perfect in Moroccan tagines, is what turns British piccalilli a toxic yellow. Today we call this 'fusion', but this modish term does scant justice to the highly complex cross-fertilization that has occurred over centuries.What it does describe, though, is the more recent trends. Chef Peter Gordon might not be the first to point out how Italian risotto depends on rice from Asia, but the 'godfather of fusion' is one of the first to deploy that argument to defend his use of lemongrass in the dish. As a result, his pioneering approach has been a key driver of culinary and behavioral change.

Tourists came looking for 'British spices' to take home as souvenirs

"Basically, Peter's view was you could use what you wanted, so long as it tasted good," chef Anna Hansen (Gordon's former protégée and the highly respected founder of Modern Pantry) has said. There, she continues to spurn heritage and tradition to create bold, innovative combinations of food from around the world. Her dry stores are fundamental – "Different pickles, vinegars, sauces and spices add the difference to the dish, and they are there all year round," she says – but her basic ingredients are fresh, local and seasonal. She might be a child of Peter Gordon, but she knew her first employer Fergus Henderson's 'fresh, simple, nose-to-tail' philosophy first.

Looking back, it seems Anna's story is representative of London's own evolution: from a place where 'spicy' meant 'cheap curry' to a true modern pantry. This, coupled with a renewed effort to support local, sustainable producers, has breathed new life into a food scene which just a few years previously would have dismissed 'spices' as largely the preserve of 'Indian' cuisine.

Gone are the days when 'having an Indian' was generally a chicken tandoori with three chilli symbols on the menu to indicate heat – a hangover, says the Spice Shop's Erath, from the curry houses that proliferated in the post-WWII years. In their stead are young, speciality restaurants like Dishoom and Rasa, whose carefully built menus reflect the regional variation within India and the use of spices therein.

Rasa serves southern Indian fare; Dishoom Bombay street food – "the most authentic experience of Indian food you can have in London," according to spice importer Pritesh Mody. Its success needs no evincing: even on Monday nights queues to eat at one of its London sites are out of the door. Hot on its heels are more authentic versions of Thai, Vietnamese and Mexican – for the latter, see Wahaca founder Thomasina Miers, who has, Mody says, "changed chilli as we know it". We expect more from restaurants and we experiment more from our own kitchens, their shelves creaking with the revolutionaries' recipe books. Grandparents aside, few Londoners today who would conflate the word 'spicy' with 'eye-wateringly hot'.

"Part of our education program is to talk about our various spices in terms of flavour, not heat," explains Mody, his importing company anther paradigm of how spice has changed in London in recent years. Called World of Zing, it was in fact born as a sideline of his grandfather's long-standing business importing traditional spices for the Asian population. "I was working in the drinks industry when I began to notice that young chefs and bartenders kept asking me if, the next time my family's business went to Mexico or Thailand, they could chuck in a box of whatever random spice they were struggling to get hold of." Armed with his grandfather's contact book and his own experiences in the industry, Mody was perfectly placed to cater for the city's growing appetite for new, original and bold flavours.

Few of us would conflate the word 'spicy' with 'eye-wateringly hot' today

Dried Persian limes, pink peppercorns, naga bhut jolokia – that is, ghost chillies, the supply of which goes almost entirely to Mark Andrew Gevaux, aka the Rib Man. Selling ribs slathered in his homemade Christ on a Bike Hot Sauce, his stall has "singlehandedly put the naga on the map", enthuses Mody. "We've sold more to him in one go than we have in two months." How the man hasn't burnt off his fingertips, we will never discover – but, like Pitt Cue, the Joint and the entire smorgasbord of street food stalls and pop ups, the Rib Man is a textbook example of a creative chef using spice in new ways to deliver great food at a reasonable price.

Mody attributes it to the recession. Post-2008, 'conspicuous consumption' – that is, fine-dining for fine-dining's sake – was a luxury few could continue, he argues. "Most people, if they were eating out, wanted value for money: big on portions, big on taste." They needed affordable fulfilment – something street food from around the world could provide by the boxful. Burritos, pad thai, dhall, banh mi, ribs, katsu, jerk chicken – all could be attained via British ingredients, provided importers like Magali Russell, Philip Erath and Pritesh Mody could source the spices.

Increasingly the direction is two ways. As demand and interest continues, the three are also influencing trends in spices. "Often, if cooks or food writers are looking for ideas, they'll come in here and I'll show them something I find interesting," Erath explains. "If they like it, they'll cook with it. Next thing you know, it's got a following." It was his shop – and his mother, Birgit – that helped inspire a young Jamie Oliver way back when, and he continues to do so.

Over at the bar, meanwhile, Mody's experience in the drinks industry is serving him well. "I've just sent a new root spice to Square Root, who make soft drinks in Hackney," he says, happily. "They're experimenting with it." He supplies the cinchona for their tonic water, too. His most recent venture, creating barrel-aged cocktails and infusions from his spice collection in collaboration with drinks consultants Fluid Movement, is going from strength to strength. "Bartenders are increasingly following chefs by creating their own drinks, rather than buying and mixing them."

It's an order of play Mani Genovese, from speakeasy Purl London, confirms somewhat reluctantly. "We're supposed to dislike each other, but there is a strong connection. New spices used in kitchens eventually tend to make their way into the bar." He shows me his spice store at Purl: jars upon tubs, crammed into an alcove and filled with all manner of flakes and powders. Experiments with wasabi have yet to work (his eyes water just telling me about it) but the cocktail of dried coriander seed, homemade ginger syrup and rum he whisks up is a far and flavoursome cry from the sugary coloured mixers of the '80s and '90s.

London's spice enthusiasts – in pictures

Genovese sees infusions of 'bark' spices, like cedar wood, taking off next, while Mody and Erath look to the resurgence of independent distilleries as the next step for spices. After all, one of the best loved spirits in a bar's armoury is vodka infused with juniper and other botanicals – that is, gin.

"There are more than 500,000 possible botanicals," Ian Hart of Sacred Spirits Company tells me. "Provided juniper is in there, there's no limit to what you can make gin with." If it's obtainable and looks like it might work in a martini, chances are he's tried. His north London distillery has used cardamom, coriander and even Christmas pudding spices for gin. He's made mistakes, but who hasn't? "If you don't experiment you don't come up with something new," he says, simply. It's a lesson no one, not even the head chefs, can afford to forget, for we have so much further to travel.

Of those foodies I've spoken to, the most influential are those constantly pushing the boundaries. Chocolatier Paul A Young refuses to rule anything out – and in spice and chocolate he has a pretty tough brief. By experimenting in his Soho kitchen, the confectioner has discovered that chai spice, smoked paprika and even a voatsiperifery pepper bring out the best in good chocolate. "I like to try everything," he says. While the rest of us are still getting our heads around the idea of a basic chilli-flecked chocolate, Young is pondering peppercorns. "Chilli in chocolate is out and Persian spices are in."

Provided juniper is in there, there’s no limit to what you can make gin with

Which brings us to Rabah Ourrad: alumnus of the Michelin-starred Ledbury and founder of Wormwood restaurant in Notting Hill. He's one of the Spice Shop's regular customers, touted to get his own Michelin star this year – and is by far the most critical of the city's spice status quo.

Every week the Algerian-born chef roasts, grinds and blends whole fresh spices – and is intrigued by the reactions of customers to his dishes. "I've discovered from this first year that using spices for unique flavours and putting them in relief, as first notes or second notes that hit the palate, made the food taste different or surprising to most of our guests," he says, "and that brought me to this conclusion: spices, especially North African ones, are still to be discovered – or more precisely to be rediscovered here."

Back in the Spice Shop, Yaziz is unpacking the last of the day's delivery boxes: a medley of Korean spices – a recent trend – and some basics. Upstairs, the combined aroma of 2,500 spices, so intense when I first walked in, has begun to subside. Suddenly, Philip and I hear her exclaim excitedly, and run up to the shop floor. "I have it! The answer to your question,' she grins. "If food is the heart of a meal, then spice is the soul." ■

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