Few people embody the sea change in fashion the way Simon Porte Jacquemus does. He grew up on a farm in the south of France then moved to Paris in 2009 as a self-taught designer at the age of 18. With no links to high fashion, he set up a small ready-to-wear label, Jacquemus, in his mother's name, building contacts one Facebook direct message at a time. And facing both scepticism and adoration from the critics, he became Tumblr famous then legitimately famous, winning an LVMH Prize and building a business worth €5m (£4.5m). Now, his growing global fanbase includes Rihanna, Solange, and some of the fashion world's most powerful editors and buyers.

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Simon Porte Jacquemus

When he moved to Paris, it was a city known for its legendary houses. Now it's also known for creative upstarts who have grabbed a seat at fashion's gilded table after rising up from the fringes. 'I opened the door for that,' says Simon, who online publication The Business Of Fashion last year called 'the hottest young designer in Paris'.

That's a big statement for a 26-year-old, but he's kind of right. It's been decades since Paris has seen this much new talent make this big an impact. 'When I started showing my collections with my friends, I became popular in the press because it was a new moment for Paris Fashion Week. Everything was so bourgeois and businesslike before, and I started with nothing. I wanted to create something for the new kind of French girl I wasn't seeing on the runway; the girl who can see the modern poetry in a white T-shirt. Now Paris has become very much about the new designer. This is good for Paris and the big houses.'

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Jacquemus spring/summer 17

He's talking about the squad he's come up alongside, most of them now superstars: Demna Gvasalia and Lotta Volkova (the respective Creative Director and Stylist behind Balenciaga and Vêtements) and DJ Clara 3000 (Simon's muse, Vêtements collaborator and the woman behind some of Paris' best parties). Often referred to as the group of creatives shaking up Paris, they each have a simplicity and earnestness that belies their cool, conceptual work.

'It wasn't calculated,' says Simon, who many call the most cheery of the bunch. 'In the beginning, it was just a group of friends. Everyone became popular much later.' Even now, with a team of 25 people behind him, the line remains a friends-and-family operation.

When I meet him, several days after he shows his SS17 collection – an elegant, poetic mix of voluminous tailoring, pastoral dresses and rustic shirts with leg of mutton sleeves – his studio heaves with retailers and editors who have travelled out to the 12th arrondissement to wish him well after what critics have called his strongest show to date.

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Theresa Marx
Jacquemus ss17

But it's his team of friends that establish the warm tone in the place. His best friend Marine made the cheese and herb biscuits he offers me. The woman modelling the new collection in his showroom is an old pal, Marion. And his boyfriend Fabien looks after the sales. 'We don't add employees – we add family,' he tells me over the phone a week later. But he's quick to clarify: 'I don't see myself as a collective like Vêtements does. I know it's very fashion to use this word, but we're a collective in life, not in terms of the design. I'm designing me and my truth.'

Fashion can be brutal for the Next Big Thing. After you've shown your first five collections and won a prize or two, the cycle moves on, hungry for someone new. In the case of Simon, you get the sense it's his tight-knit support network that keeps him inspired and his confidence rock solid.

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His mother Valérie first opened his mind to the idea he could design clothing for a living. 'I was seven and had cut one of the kitchen curtains down and turned it into a skirt. My mother liked it so much she wore it to take me to school. I saw that it's possible to do this as a job,' he says. She passed away aged 42 in 2008, the year he started his business.

He's been mining the lessons learned from his family and his childhood memories on their farm ever since. His brother, Félix, built his ecommerce platform while his father Vincent built his showroom's racks. 'My childhood and the south of France will always be the bedrock of my work. I live in Paris, but I will always be a south of France boy,' he says.

Simon says the only outside investment he's had is €150,000 (£163,061) from the 2015 LVMH award: 'We paid for all of the clothes on the racks with what we made from past collections.' His clothes may have a recurring thread of childlike naivety, but their popularity rests on his sophisticated ability to slay digitally: he counts Net-a-Porter, Browns and MyTheresa among his online stockists.

'Thanks to his innovative approach to classic silhouettes and the brand's contemporary price point, his pieces sell out almost immediately,' says Sarah Rutson, Vice President of Global Buying at Net-a-Porter.

An exclusive Jacquemus capsule collection for the e-tailer goes on sale this month. His clever advertising campaigns, such as one that didn't feature any clothing, but instead photos of Simon as a child, go viral while his Instagram is a regular on follow lists. And unlike most designers in the industry, he can't remember a time in his professional life when social media didn't exist.

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AW16 Jacquemus, out in the wild

'It has always been important to me. The internet made me famous, and I get feedback from my consumers every day.' He says he learned the power of self-made celebrity when he saw Jean Paul Gaultier on TV as a boy. 'The way he did clothes with a smile and humour – I felt close to that. I could see he wasn't bourgeois so I thought, "I'm not bourgeois. I'm going to do fashion too."' Now, it's Simon who all the would-be Next Big Things look up to. 'I don't want to sound pretentious, but I hope I've become that inspiration for other people,' he says. We'll just say it for him.