Long before Stella McCartney became one of the most innovative designers of her generation, before she’d dressed Olympians and A-listers, and Meghan Markle in that white halter-neck reception dress that set the internet alight, she had to graduate from design school. A vocal vegetarian and animal rights activist like her parents (Sir Paul, the musician, and Linda, the photographer/musician/entrepreneur), Stella decided at the age of 12 – the moment she resolved to be a fashion designer – never to use leather, fur or feathers in her creations. For a luxury fashion designer to turn her back on leather is like a guitarist boycotting the C chord: a lion's share of the luxury industry’s profits come from leather shoes and bags, often as gateway purchases to customers whose budgets wouldn’t normally stretch to ready-to-wear. Nevertheless “it wasn’t even a question as to whether I’d make them in leather”, McCartney says.

It was 1995, and McCartney was studying at the prestigious Central Saint Martins design school, in London. The graduate show involved eight looks, each requiring footwear. “I worked really hard at that,” she recalls. “It was hard enough to find someone to make shoes with no minimums. When you’re a student, it’s virtually impossible. That’s why virtually every design student just has a pair of Tesco shoes on the runway.” But McCartney searched and searched until she found a shoemaker willing to help make her eight pairs in animal-friendly fabrics to match those in the collection.

The show, when it finally arrived, was a sensation. McCartney asked her friends Kate Moss and Naomi Campbell – who just happened to be the most famous supermodels in the world – to walk the runway. Her parents sat in the front row; her dad had composed a new song for the occasion. The show made the pages of the New York Times. Her father and Campbell were quoted. Stella was not. The shoes and the clothes didn’t even get a mention. But that’s not the point of the story. The point is: she didn’t compromise. She found a way to make the shoes.

McCartney didn’t compromise again when, two years later, she was appointed creative director of the struggling Paris fashion house Chloé. She was 25 years old. Not even when the entire industry criticised her appointment (Karl Lagerfeld: “I think they should have taken a big name. They did, but in music, not fashion”). She didn’t compromise when – having revived Chloé’s fortunes, reportedly quadrupling sales in the process – she left Paris in 2001 to set up her own label in 50-50 partnership with the Gucci (now Kering) group. Her friend, the designer Tom Ford, once gave her a tour of his studio, extolling every kind of dead-animal skin, trying to change her mind. That didn’t work either.

In fact, she redoubled her efforts, appearing in campaign videos about the cruelty of the leather and fur business, which were circulated among the designers of rival luxury brands. And, as she learned about the environmental impacts of the fashion industry – global textiles production emits1.2 billion tonnes of greenhouse gases annually, more than international flights and maritime shipping combined – she set herself stringent sustainability targets, like using organic cotton, avoiding endangered forests, and reducing her use of oil-based synthetics. Every time she was ignored, or criticised. “It was met with aggression, or defensiveness, or being ridiculed,” she says. “I didn’t feel criticised, because criticism feels valid. I grew up my whole life facing that.”

Stella McCartney is telling this story in late September 2018, on the third floor of her new flagship store in London’s Old Bond Street. A beautiful grey wool overcoat, drop-shouldered and oversized, envelops her like a duvet; on her feet are a pair of uncannily real-looking black and white faux Croc heels. The store opened in June, one of more than 60 worldwide, and is a monument to sustainability. The mannequins are largely biodegradable sugar cane. Ecotricity supplies the store with green energy that is primarily wind power. One wall is decorated with paper pulp recycled from the shredder in the company’s head office. The air is among the cleanest in London, thanks to an innovative filtration system designed by the clean-air startup AirLabs.

McCartney is no longer ridiculed. In late 2017 Gucci announced its intention to go fur-free, as have Burberry, Versace, Calvin Klein and Armani – and the luxury online commerce company Yoox Net-A-Porter. Meanwhile, Stella’s business is booming: recent UK sales were up 31 per cent, and profits 42 per cent. So much so that, in March 2018, she bought out Kering’s stake, bringing the company back under her full control.

“It’s astonishing how it’s changed in my lifetime. If you look at the past week alone, LA has gone fur-free [the city had just banned its sale], Berkeley has gone vegetarian. London Fashion Week was fur-free this week. Helsinki [Fashion Week] is leather-free. I mean, what the fuck? In one week?”

Stephane Jaspar, her chief marketing officer, is lingering nearby on his phones, and leans into my dictaphones: “Emphasis on: what the fuck.”

McCartney grew up in nature: to avoid post-Beatlemania, her parents moved the family to farms in Sussex and Scotland, where they lived with a menagerie of animals. “What kid doesn't love growing up in a field, with sheep around, or riding a horse, or watching dragonflies? Those are my best memories as a child. More so than going on a private jet to Brazil to go and see [her father perform at] a gig with 200,000 people,” McCartney says. Her weekends would be spent hanging out with some of the greatest artists of the 20th century: George Harrison, Michael Jackson, Stevie Wonder, David Bowie. Those were amazing memories, but the real foundations of what I look back on would be in the countryside with my siblings and my mum and dad.”

The McCartneys sent their children to state schools, and McCartney tried hard to avoid being associated with her parents’ fame, going by the name of Stella Martin. As she rose in the fashion world, snide observers (and rival designers) would allege her success was down to her parentage – even though a survey of famous people’s children reveals few such success stories. “I think being Paul and Linda McCartney’s daughter makes you a bit like, you know what? Fuck you. I can show you a kid of substance. That could have been one of the factors that drove me: to prove to people that it wasn't because of who my parents were that I got a job, or that I got into a room,” she says. “Or prove to myself, maybe.”

For McCartney, the design process as often starts with a material as it does aesthetic inspiration – a song, an image, an emotion, a silhouette. That is in part a result of working with such stringent self-imposed limitations. “For example we don’t use PVC, which a lot of other houses do,” says McCartney. (Polyvinyl chloride, a plastic used in shoes, outerwear and details like sequins, is highly toxic.) “So when I go, ‘I want a lot of sequins this season,’ everyone else has this many …” – she spreads her hands, shoulder-width apart – “… whereas I have this many” – a hair’s breadth. “So then your challenge creatively is how can I make the most of that?”

“All of the designs begin with the fabrics,” says Claire Bergkamp, the company’s worldwide director of sustainability and innovation. McCartney hired Bergkamp in 2012, to help transition the entire company to a more sustainable way of working. One of her first projects was working with the Kering group on the company’s environmental profit and loss report, which measures a company’s negative impact on the environment. “Four or five primary building blocks make up the majority of the collections,” she says. “We use a lot of viscose. Wool we use a lot of, cotton we use a lot of. For bags and shoes we use a fair amount of polyester. It's been about: how do we improve the sustainability of each of those building blocks?”

One of Bergkamp’s first breakthroughs was with viscose, or rayon, a commonly used luxury fabric spun from wood pulp. Every year more than 150 million trees are felled to make viscose, often from endangered forests. Working with Canopy, a global forestry NGO, Stella McCartney became the first brand to guarantee its viscose is verified from sustainable sources. Bergkamp personally visited all the sites on the supply chain, shook the hands. The process took three years. For fashion houses, which can often start on a new collection only weeks or months before the runway, such a laborious development process is virtually unheard of.

“When it comes to sustainability, she is lapping other designers,” says Nicole Rycroft, Canopy’s executive director. “Stella was the first brand to cancel a contract with a viscose brand because it was using an endangered forest. She was the first real recognisable global designer to adopt Canopy. The thing that impresses me most about Stella the person is: she walks the talk. As a result of that, 160 brands have followed suit.”

When Stella and her design department want a material – for a lace gown, a ruffled shoulder, an embroidered detail – Bergkamp’s team sets to work. “You go to the design team and say, can I have some devoré velvet this season? And they say, well you can in two years,” McCartney says. Over the last five years, they have built an exhaustive database of suppliers and mills capable of reaching their exacting standards of quality and sustainability. “We tend to work with mills over and over again, so we work with them on getting organic cotton in, on getting traceable wool in, getting recycled material in,” Bergkamp says. “I spend a lot of time convincing suppliers that I'm not insane, so that when we ask them to use organic cotton they don't tell me to fuck off. Because, you know what? For a long time, they did.”

The racks of a Stella McCartney store are a pageant of luxurious deception: beautiful, buttery “leather” jackets and bags made from a fabric it calls Skin-Free-Skin (polyester and polyurethane, coated with vegetable oil) hang alongside leopard-print Fur-Free-Fur (spun from organic fibres). Pumps glisten in seemingly every skin imaginable. It’s I Can’t Believe It’s Not Butter! for dead things.

On the third floor, where we’re having our conversation, is an exhibition dedicated to the Loop sneaker, which McCartney launched in August 2018. The Loop has a starkly minimal, sock-like upper, which is woven-knitted to reduce material waste. But the real innovation is in the sole. In regular sneakers, the sole – usually made from non-biodegradable, oil-based polymers like EVA (ethylene-vinyl acetate) or TPU (thermoplastic polyurethane) – is glued permanently to the upper, making recycling nearly impossible.

Recycling has become an obsession with McCartney. In recent years the brand has worked closely with the Ellen MacArthur Foundation, a leading advocate for the circular economy: radically reducing the environmental impacts of consumption by recycling as much material as possible and obsessively reducing waste. “Every year we produce 53 million tonnes of fibres to make clothes and textiles and every year we landfill or burn 73 per cent of those fibres,” Ellen MacArthur, the celebrated yachtswoman, told me. “It’s a staggering figure that shows our fashion system is broken, and cannot ultimately continue to operate the same way.” That waste is being exacerbated by the rise of “fast fashion”. Since 2000 the amount of clothing produced worldwide has doubled, but the number of times an item is worn has fallen by almost half. “Right now we design, make and use clothes in an almost completely linear way,” MacArthur says. “We take a material, we make something out of it, and then, in the majority of cases, it gets thrown away.”

For the Loop, McCartney wanted to design a shoe that could be recycled in its entirety. “We wanted to make the most glueless shoe possible, which is unheard of,” McCartney says. The solution, which required 18 months of development from McCartney’s product team, is ingenious: the Loop’s midsole is attached to the upper via a system of moulded interlocking clips, and then sewn together, meaning that at any point the sole can be removed, recycled and replaced.

It’s an innovation that you might expect from a global sneaker giant or a Silicon Valley startup, rather than a luxury fashion house. (Although, at £485 a pair and upwards, it’s priced as a luxury item.) “There’s a lot of shoe companies that haven’t done this because maybe they didn’t have the idea, which for us is based in sustainability. The starting point is not design, the starting point is sustainability.” McCartney points out that when the design team was developing the sole’s clip mechanisms, the materials really would break the mould.

Stella McCartney HQ, in London’s Shepherd’s Bush, is an elegant, white-walled building in the shadow of the Westfield shopping centre. Bergkamp had just returned from a trip scouring startups on the US West Coast. In recent years, thanks to breakthroughs in biotechnology, a number of innovative materials startups have emerged, promising eco-alternatives to animal products: meat-free burgers, egg-free eggs, and lab-grown leather. Much of Bergkamp’s job involves meeting those who might offer new materials for McCartney’s repertoire.

McCartney and Bergkamp had long wanted to find an ethical alternative to silk, which is produced by boiling or gassing silkworms and harvesting their cocoons. In 2015 Bergkamp came across Bolt Threads, a startup that had made a breakthrough in developing synthetic spider silk. In materials science, spider silk has long been seen as a super material: simultaneously incredibly strong, elastic, biodegradable and hypoallergenic. “Spiders are fascinating,” explains Bolt Threads’ CEO and co-founder Dan Widmaier. “When humans spin fibres, we use a century’s worth of engineering knowledge. The spider, by contrast, is very elegant. It doesn’t have access to temperature, pressure, harsh solvents. It has water, whatever temperature it is outside and almost no musculature.”

Widmaier and his co-founders, David Breslauer and Ethan Mirsky, copied the way spiders make silk. Their product, called Microsilk, uses bioengineered yeast to produce the silk proteins, which are then extruded and spun into a fibre. When Bergkamp and McCartney visited their headquarters in Emeryville, California, it looked more like a brewery – with huge fermentation tanks, and technicians in white coats – than a textiles factory. (At one time, spiders roamed free-range around their office. “If you keep them in a cage they can't make a web,” Widmaier explains. They also ate each other.) “I was blown away,” says Bergkamp. “They were considering the same things we’d want to be considering at the beginning. How would you dye this? How much energy is required? How much waste is going to be created?” McCartney has called the trip a “life-changing and career-changing moment”.

“[Stella] showed up, and her team actually thought about it differently than anyone else. They said, ‘I don’t have a product in mind; I’m just going to play with it, see what it can do.’ They were much closer to the agile mindset that we know as a startup,” says Widmaier.

In July 2017 McCartney unveiled a gold shift dress made with Microsilk, for display at the Museum of Modern Art in New York. The two companies are developing the material to be ready for mass production in the next few years. In April 2018, the brand also unveiled a second collaboration: a special edition of McCartney’s bestselling Falabella handbag made from Mylo, a leather alternative bioengineered from mycelium – fungus roots.

“We want to be the house of technology,” says McCartney. The company has recently sponsored Central Saint Martins’ Material Futures degree course, and the animal rights charity Peta’s Biodesign Challenge, a global competition to find eco-conscious materials. “Technology is, for me, the future of the conversation that we started in the fashion industry a very, very long time ago.”

The Bolt collaboration is just one of a number of partnerships the brand has signed with startups. Some partnerships, such as with Colorifix, which makes bioengineered non-toxic dyes, are public; most are not. “Why we’re desirable I think, as a partner, is because we’re small,” she says. “We have amazing relationships with our suppliers, so we can tie them into supply chains a lot quicker than some of the bigger companies. We do have an extremely high standard for quality – if they can meet our requirements, then it’s good enough for everybody else.”

Although the environmental credentials of Stella’s brand are substantially further ahead than the rest of the industry, she has set Bergkamp aggressive targets to hit: to eliminate all industrial waste and to exclusively use recycled polyester from the textiles industry. “One per cent of clothing is recycled back into clothing. That means everything that is being produced in the garment industry right now is waste, basically,” Bergkamp says.

Her greatest challenge is polyester. Produced from oil, polyester constitutes 55 per cent of all textiles produced worldwide. Virtually every high street T-shirt you buy will have polyester blended in to reduce costs. The material takes over 200 years to biodegrade. Recent studies have shown that every year around half a million tonnes of plastic microfibres leak into the ocean from washing synthetics – the equivalent of more than 50 billion plastic bottles.

This is especially problematic for McCartney, because most of the brand’s innovative synthetic leathers are made from polyester, with a polyurethane and vegetable oil coating. (The brand claims the carbon footprint of its vegetarian leathers is still 24 times smaller than that of animal skins.) “Polyester is a big one for us,” admits Bergkamp.

The brand already uses polyester recycled from plastic bottles in much of its clothing, and is on track to replace all its nylon with Econyl, which is made from recycled fishing nets, by 2020. It is currently working with Evrnu, a Seattle-based startup that has developed a process to recycle cotton into a cellulose-based fibre; McCartney hopes to debut it in 2019. “We’re looking for companies that can break the materials down to their basic building blocks and build them back up,” explains Bergkamp.

It is also working with TIPA, an Israel-based startup, to switch all its plastic packaging to biodegradable, plant-based alternatives. “With real trendsetters, it’s about more than business,” says TIPA founder Daphna Nissenbaum. “Stella is independent of the market. She would do it even if nobody else was.”

McCartney admits the brand still has some way to go. “When you start trying to have a conversation about business, people basically want to go, drrrrrrrr” – McCartney mimes a machine gun firing. “It’s like: fall down! You’re fucking lying! I’m so aware of that. We’re not perfect. We don’t want to use silk, that’s why I’m talking to Bolt Threads. I’m trying my best. Something is better than nothing.”

She points to the Loop sneaker again. “That took 18 months to develop. I paid for it myself. There’s zero encouragement. There’s no government policy. Nobody has given me any incentive to do this. But I’m still doing it. So if I’m doing it, anyone can do it.”

A few days before our interview, McCartney launched her own version of Adidas’s bestselling Stan Smith sneaker. Few details (other than the price, at £235) stand out at first: the shoe’s iconic three stripes are replaced with stars, a McCartney motif (stella, star). Her face is illustrated on one tongue, opposite an image of the tennis champion Smith, who himself attended the launch party – as did Madonna, Riz Ahmed, and Anna Wintour.

The Stan Smiths’ ordinary nature is entirely the point. The shoes’ real innovation is designed to be invisible to anyone who doesn’t know: it’s an entirely vegan shoe. The leather upper is synthetic. The glues were replaced with animal-free alternatives. “We pushed to get it vegan and they let me. And we did it. I’m so proud. That is fucking – it’s the future,” she says.

McCartney has a close relationship with Adidas: she has designed a sportswear line for them since 2005, as well as serving as creative director for the Team GB Olympic uniforms. The brands share an environmental focus: Adidas is developing biodegradable sneakers, and makes an increasing number of products using recycled ocean plastic. Several years ago, the brand made a one-off pair of vegetarian Stan Smiths for McCartney as a gift. “I said to the CEO of Adidas a couple of years ago: why don’t you make all your Stan Smiths vegetarian and not tell your customer? Can you imagine the impact environmentally if they just did that one thing? Me, I would do it like…“ – she clicks her fingers. They demurred, so she asked to do it herself.

For McCartney, deceiving her customer is the highest praise. “I relish the thought that 99 per cent of our customers come in here, and they see the Stan Smith, and they haven't got a clue it's a vegetarian shoe,” she says. Because if customers can’t tell the difference, then there’s no reason to kill animals any more.

But also, as a designer, McCartney lives and dies on the desirability of her creations. “That’s my job, first and foremost. If I don’t design things that are desirable, and sexy, and a must-have for people, then it just ends up in landfill anyway.”

Once upon a time McCartney's vegetarianism was the fringe. Today veganism is fashionable; electric cars are the new supercars; and every major fashion brand is suddenly talking about sustainability. “I'm sitting here in the last few months, thinking: this might be happening. It's overwhelming for me. Honestly, I could almost cry,” she says. But she doesn’t cry; in fact, enveloped in her giant coat, McCartney doesn’t seem happy. She seems angry.

“I’m not angry,” she says. “I might have been a few years ago. I can get frustrated and I can get disappointed, in that 90 per cent of the environmental issues that are mentioned in the fashion industry are based around marketing. They’re not really heartfelt. They're not really genuine.”

As a test of whether companies have really changed, McCartney says: “Try changing something your customer doesn’t see.” Because for every major product, like the Loop sneaker and the Stan Smith, there are countless stories that McCartney doesn’t announce. “The spring/summer collection in January was the first time we had a clear plastic since we stopped using PVC in 2010. It took us eight years,” says Bergkamp. “That was a huge deal! But we didn’t make a big deal out of it. The summer collection last year is the first time we had taffeta, made out of recycled polyester. Nobody would ever know that. We don’t talk about stuff until we mean it. We don’t just market stuff to market it. It comes from Stella. This is not bullshit, this is real company strategy.”

When I ask McCartney what keeps her so motivated, she replies: “As a designer you're never going to think you've done the best collection. There's never an end of the journey. I look at that” – she gestures to the Loop sneaker – “and say, 'It's practically glue free!' And Stephane [Jaspar] will be like, ‘Actually, there's the minimum amount of [animal-free] glue’ – and there's this whole technical rampage of reasoning. So I’m like, ‘OK, that's not finished then.’ But that's great. Isn't it great? I don't want to be finished. I want to make it better.”

This article was originally published by WIRED UK