Forget the keening sirens. Shut out the rumble of trains overhead. Ignore the filament bulbs, the indie soundtrack, the pierced, pink-haired dude Deliverooing a pizza. You know you're not in a château in the gentle, luscious hills of Burgundy any more when the winemaker you're chatting to draws a direct line between gynaecology, male prostitutes and wine. "To me, sommeliers are the gigolos of the wine business," says Warwick Smith, with the sort of irreverence you might expect from the founder of a winery called Renegade. "They've been around. The winemaker, though, is the gynaecologist: he knows the ins and outs. He knows what's going on behind the scenes."

He takes a sip of a 2016 barrel-fermented sauvignon blanc – aged, blended and bottled here in his Bethnal Green winery, and continues expansively. "They're both skilled: the sommelier in tasting notes, food pairing and communication, the winemaker in chemistry, logistics, technique – but they're very different gigs."

Renegade London wine's founders Warwick Smith and Josh Hammond

Renegade London wine's founders Warwick Smith (left) and Josh Hammond (right)

Warwick should know. A former marketer, he actually trained as a sommelier before establishing Renegade winery under a railway arch in East London. At the time of opening – spring 2017 – they were only the second winery in London. Now there are four: Renegade, London Cru, Blackbook Winery and Vagabond Urban Winery.

Each one considers themselves innovative – and they are, almost by default, for who in their right mind would make wine in the heart of one of the world's most crowded cities, where traffic is terrible and space costs a fortune? Who but a madman, or at the very least a creative, would drive a lorry full of grapes all the way from, say, Piedmont in Italy, to Battersea Power Station or Earls Court?

"One of the reasons I didn't do this a long, long time ago is that it doesn't make any sense, this model," says Smith. "You can only make a limited amount, because you can only afford so much square footage, and you're competing with supermarkets." One commonality these otherwise diverse London wineries share is an overriding anxiety about balancing the books.

To an extent this dictates the style of wines they can make. Space counts for nothing on the Iberian Peninsula. You can store barrels for years without thinking it's costing you more in rental fees than you might make back when you bottle it. But in Battersea, making a sparkling pinot noir, aged for four years on the lees so you get that brioche character, is hard to justify from a cash-flow perspective.

"It's just sitting there," says winemaker Gavin Monery. Five thousand bottles squatting on several hundred grand's worth of prime mixed-use property for four years, without earning a single penny.

So why do you do it? I ask Monery who, in the employ of Vagabond, has just opened a winery in the back of their latest branch in Battersea Power Station. Prior to this, he was at the city's first winery, London Cru. "The key thing is people. It's telling our story, getting people involved in the process." Take away the people – the residents and employees of Battersea, Vauxhall and Pimlico – "and it's just a really expensive place to make wine in."

Vagabond is many things: a wine shop, a restaurant, and a wine bar with an innovative tap system allowing customers to try even quite pricey wines by the glass or tasting measure. Thus far it has proved incredibly popular. Yet with the growing success of English wines and vineyards, and London Cru spearheading urban winemaking just down the river, Vagabond's founding director Stephen Finch saw an opportunity to get in on the expanding English market while furthering his customers' engagement and understanding of winemaking.

"The reasons we opened a winery in London back in 2013 were twofold: we believed we could make quality wine in London, and we wanted to bring people into the winery."

I'm speaking to Lindsey Marden, London Cru's events manager, within the fine surrounds of their newly renovated tasting events space. The gleaming oak table is made of old sleepers they used to rest barrels on, and stumps of ancient vines, gnarled and withered into artworks, are dotted about the room. The unit is custom made from vintage French wine crates. There's money here, that much is clear – the winery is owned and backed by wine merchant Cliff Roberson, of Roberson Wines – but there is creativity too, and it goes well beyond this oak table. After all, London Cru pioneered urban winemaking. They were the first to look at the popularity of French vineyard tours, the prevailing trend for gastronomic experiences, and conclude that what well-heeled, wine-loving Londoners were gasping for was their own wine and winery.

Of course, there's no denying that being part of Roberson Wines gives London Cru an element of economic stability. The Roberson offices are upstairs. Tastings, corporate events and workshops are held down in the winery. Vagabond, too, has a firm financial foundation in the form of its highly successful collection of wine shops and bars. Though the names of the four wineries all imply a maverick attitude, it is Renegade that is taking the biggest financial risk. "I've re-mortgaged my flat to set this up. If it works, then brilliant. If it doesn't, I'll lose my flat," Smith smiles dryly.

For some, this would be a hamstring; but for Smith, it's an artistic license. "I am not owned or employed by anyone. We're not trying to be gimmicky – and there is a balance to be struck between being different and independent and being gimmicky – but within that I can do whatever I want."

He points to a stout barrel, squatting by the bar, labelled 'Warwick – Don't Open.' "That's my little toy: English seval blanc, pinot noir traditional champagne-method English sparkling wine fermented in Kentucky whisky barrels."

How's it tasting? I ask. "Well, at the moment, like Jack Daniels and lemonade with a wine-y twist," he laughs. "But it will be very different after it's been in bottle for a year." Though he and his winemaking partner Josh Hammond played fairly safe when they first opened, Smith soon realised there was no point in following the rules and "making the same style of wine as those you can find in Tesco for six quid."

Out went sterile filtering, sulphites, dosage (the addition of sugar to wine), and the practice of cold stabilisation to make the wine clearer. In came natural fermentation methods and wine blends spanning not just regions, but whole countries: a sauvignon blanc made from Bordeaux grapes with a yeast strain predominately used in New Zealand; a rosé marrying grapes from Spain, England and Italy. Renegade weren't the first to pioneer cross-country blends: that accolade must go to London Cru, whose 2015 King's Cross blend marries grapes from France, Spain and Italy. But they are the first to really celebrate this approach as a distillation of the diversity and creativity of London – as well, of course, as a means of making great wine.

the human terroir captures personal preference

Their rosé is unapologetically billed as 'the anti-Brexit bevvie – a multi-cultural juicy number.' "We drink beer made from New Zealand hops, German grain and English water," Smith points out. "We eat Argentinian steak with French béarnaise sauce. Why don't we mix grape nationalities?"

In part this is down to the taste of the individual winemaker: Smith is – well, a renegade, seeking to disrupt the market, while Gavin Monery and London Cru's Agustin Novoa are all fairly classically trained. Monery cut his teeth in his homeland, Australia, then worked for various producers in France as an assistant before setting up his own small vineyard in Burgundy. Novoa, London Cru's new winemaker, specialises largely in the wines of cold climates – Germany, Austria and now England – despite his Argentinian heritage.

In a traditional sancerre, forged by a winemaking dynasty in the centre of the Loire, for example, you can taste the physical terroir: the verdant valley, chalky terre blanches and the ambient, river valley climate. Yet while there's no such terroir in London – "that takes place wherever the grapes are grown and picked," says Monery – there is still the "human terroir, which people don't often speak about" he continues: one which captures the personal preferences and techniques of the winemaker, his boss (if there is one) and his clientele.

Smith leans toward richer, more intense wines, with a slightly higher alcohol content than those at Vagabond. He ferments in steel, or a Georgian wine making vessel called a queverie, or barrels of all ages and varieties.

Monery likes fresh, lighter wines "which, I hope, are slightly elegant in style." It's no coincidence that Vagabond and London Cru age their wines in French oak barrels, for instance: it's Monery's legacy – and there is a "recognised quality" to French oak which has a broad, timeless appeal.

"French oak is what Gavin favoured, and Ag likes them too," Marsden continues, as we browse London Cru's barrel rooms." You won't find old bourbon barrels lurking in one of these smart chambers. For Roberson, quality is the first and foremost consideration. They've a reputation to uphold. "Cliff (Roberson) has been in the business for 30 years. He is a professional. He only wants the absolute highest calibre." In response, his winemakers have created a series of accessible, award-winning and beautiful wines.

Then there's the fruit they use: a question of taste, and the winemaker's relationship with different growers. Though most of their early wines used European grapes, London Cru have decided to stick solely to home-grown fruit henceforth: Agustin Novoa has strong contacts among English growers, and a particular facility with cold-climate wine.

Monery, too, favours English grapes, but suggests the pressure to create wines that would prove popular with Roberson Wine's large and diverse customer base – London Cru is not a bar, and their wines are largely sold to restaurants via Roberson's or on their website – didn't lend itself to great experimentation. "I could never have made something like this," he says, bursting a bottle of what looks like cloudy lemonade open with a ptzzzz and pouring a couple of glasses. This is a pétillant-naturel: "a zero-sulphur, zero-dosage sparkling wine, from the English reichensteiner grape with a bit of pinot noir," he continues. More commonly known as pét-nat, wines made in this style are bottled prior to completing their first fermentation, allowing carbon dioxide to be produced by the grapes' natural sugars; with champagne, it comes from added sugar and yeast during the secondary fermentation of the wine.

From the outside pét-nat looks still and, because it's unfiltered, quite murky. Only when you open it does the carbon dioxide come out of solution to make its sparkling appearance. It's a fun wine: light, fizzy and fairly cheap, it is "designed to compete with prosecco, really. It's not champagne, and it's not trying to be champagne," explains Monery. Yet while there's no doubt that this pét-nat will fly off Vagabond's riverside terrace come summer's long, warmish evenings, it'd be a hard sell to another restaurant with many tables and little time to really explain to customers what pét-nat is, and why the yeast is still suspended like a fine cloud through the wine.

"If things are too left-field, restaurants don't want to buy it," says Monery bluntly. After all, the moment a customer is dropping over £35 on a bottle they're likely to play safe unless the sommelier can advise otherwise. But at Vagabond, you don't have to commit to a whole bottle: their tap set-up means you can try a sample or glass, and there are staff and informative labels to take you through each of the wines. "If I'm selling to 20 restaurants, I have to make something classic. Here I can make whatever style I like, within reason, because we're not reliant on someone else selling it." What's more, by producing a wine that is quick, easy and – once you've explained the mist away – highly sellable, Money can build up the cash flow necessary to pay the rent on the longer-aged wines.

"In a way, it's like feta," he says of pét-nat – a strange analogy, until you realise urban wineries are as much at the mercy of space and finance as urban cheesemakers. "You make a young cheese like feta so you can get it out the door and get money in so you can fund the mature cheeses," he continues. He's not there yet, but in the future Monery dreams of vinifying and ageing a champagne-style English sparkling wine. It could soon be reality: Monery's cashflow comes not just from the wines they make, but from the sales and events they sell in-house and across Vagabond's four branches. That enables a degree of experimentation.

renegade's new sparkling is aged in an east end church

"We have people living nearby who see this place as an extension of their living room," he grins. "They meet us, they watch the process, they can help out during harvesting and taste the wine from the barrel as it ages." They bring money and atmosphere – but through feedback and volunteering they arguably also contribute something toward the wine.

Place matters. Smith even maintains the vibration of trains above Renegade's arch stirs the fermenting wine, creating "more contact between the lees and the juice." It might sound like a stretch to claim London's wines reflect the very different areas in which they are made, but it's hard to dismiss the idea when you visit these wineries and taste their wines. Last summer I spent the day at London Cru, helping them bottle and label their 2016 Baker Street – and while of course, the wine was finished by then and wasn't touched during the process, it still felt like we – myself and six others, many of whom were local – had brought something to that particular vintage.

"For the 2017 harvest we did an Instagram post asking if people wanted to come help make wine after work," Smith recalls. "We had 100-odd people come along to help destem the grapes and sample some wine. We're collaborating with breweries. We're teaming up with the East London Film Festival. We're encouraging people to help during the harvest. We want to bring the community," he enthuses – and to judge by the reception he's had, the community are coming. Yet even if you discount the impact locals can have on the actual winemaking, there's no dismissing the impact of local demand.

"People seem to respond in this area to wines with a more natural story: unfiltered, unrefined, vegan and vegetarian," says Smith. "They gravitate more toward funk and more differentiated styles."

That seems unsurprising in hip East London. London Cru, meanwhile, err more towards classic styles: appealing to quality restaurants, Roberson Wines customers, and their West London surrounds. You don't even have to look beyond the label: Renegade ran a competition among London artists, and chose a Dutch artist who trained at St Martin's to draw a series of fun, Ralph Steadman-esque labels for their bottles; London Cru, meanwhile, struck lucky with highly respected design agency The Partners, who produced their clean, smart, multiple award winning wine-leaf label. Battersea's clientele – that of Vagabond, and Blackbook, which I didn't get to visit – will become clearer as the power station continues to develop: but they've certainly shown an interest and enthusiasm for wine that is homegrown, and made in town.

This year, Renegade release their first blanc de noirs aged sparkling: English grapes, pressed, oak-barrel-fermented and bottled in London. They'll ferment and age in the vaults of a Hawksmoor church in the East End, where customers who pay for a bottle in advance can try their wine from the barrel during secondary fermentation – an experiential value added to justify the hefty price tag.

"It'll be the first champagne-method sparkling wine to be made in the city," enthuses Smith. Will it be more 'London', as a result of being pressed, fermented and blended here? Will it feel more 'East End' than the aged sparkling pinot noir Monery plans for Vagabond? We might never really know. "I think people don't even have a handle on what terroir means for English wine yet," says Monery – let along the more intangible cultural terroir you get once the grapes hit London. Yet as the cork of Monery's pet-nat pops off to reveal a bright, fizzing rush of bubbles and booze, I can't help but feel that for one fleeting moment London – smart, fast, busy, zany, posh, scruffy, unfathomable London – has been captured inside this wine.