Go to any wedding this year and someone will be wearing a Self-Portrait dress. Although it's likely to be its best-selling Azaelea style (strappy, midi-length and very flattering), it might also be its floor-length Mia dress as worn by the Duchess of Cambridge or even the black Nightshade look seen on Meghan Markle when she had Christmas lunch with the Queen.

Since its launch four years ago, Self-Portrait has become a go-to for feminine, flattering and modern occasionwear at an affordable price – not many of its dresses are more expensive than £300. Few could honestly say they're immune to the brand's pretty guipure lace designs and relatively affordable price points - such is the label's broad appeal that its customers are aged between 18 and 50.

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The Duchess of Cambridge wearing Self-Portrait at the premiere of \'A Street Cat Named Bob\

So what does it take to create the ultimate It dress that everyone wants? Self-Portrait founder Han Chong says it boils down to whether it not it enhances a woman's body.

"My dresses are super flattering," Chong tells us. "A lot of effort goes into the fittings. With the Azaelea, I tried it on lots of my friends and I wanted to know how they felt in it. I made sure she felt confident in it – that dress in particular offers a lot of support. A friend said to me recently, 'that dress is like wearing a really good support bra.' That's key for us – making a woman feel special."

Chong always had a clear idea about what he wanted to achieve and remained true to that goal – create feminine, well-designed dresses that were affordable.

"I always start with thinking, 'what does a modern woman want to wear this season?' I think about where she might be going, what occasions she might have planned and how she wants to feel when she's at those events or in those situations," he says. "How does she want to be received at work or at a wedding? I step into her lifestyle and try to imagine what I would want to wear if I was a woman."

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Miranda Kerr wearing Self-Portrait\'s \'Azaelea dress in December 2015

Chong's innate understanding of his customer and what she wants have served him well. Within four years, Self-Portrait has landed international stockists such as Net-a-Porter and Matches Fashion, with its most popular dresses selling out within 24 hours of going on sale. Next week, he'll open his first standalone store in London. Product categories, which began with contemporary occasionwear (a largely underserved market), now extend to outerwear, knitwear, shoes and sunglasses. His customer base is far-reaching, including Michelle Obama, Kristen Stewart, Miranda Kerr, Beyoncé and of course the royals.

"Our customers are royals obsessed," laughs Chong. "Every time Kate or Meghan wear anything, it flies off the shelves. Beyoncé had the same effect. The white dress Kate wore is still our number one bestselling dress a year on. My pieces aren't too expensive – people feel special wearing the same dress as a princess for £300.

"For a small brand that doesn't have big advert budgets, celebrities wearing our pieces really helps our position. That said, social media influencers are important too – people really look up to them."

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Michelle Obama wearing Self-Portrait in September 2016

When a certain style really captures the imaginations of shoppers, whether Caroline Constas' off-the-shoulder top, Isabel Marant's wedge trainers or Self-Portrait's Azaelea dress, the copycat versions soon follow. Yes, imitation is flattery, but not all designers appreciate it – especially when they impact sales. Chong sees it differently.

"It's inevitable in fashion when you have a popular item," he says. "But the detail isn't there; my dresses are crafted in a different way to the high street. They might look similar, but they won't feel the same. I can spot a fake a mile off, even the good ones, because my designs support a woman's body in a different way."

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Zendaya wearing Self-Portrait at the \'Hateful Eight\

Next week on 22 March, Chong will open Self-Portrait's first standalone store in Mayfair with plans to open as many as 10 shops across the US and the Far East within the next three years.

"We want to sell where there's demand and create that balance between online and offline," he says. "I always wanted our customers to see the brand in its own space. The décor of the London store is very similar to my house – I live in a very modern space with lots of concrete. I like the mix between the femininity of my pieces and the hardness of the concrete."

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Han Chong inside his Mayfair store

In the same way Chong is very mindful as to what his customer wants in terms of wardrobe, his shops are similarly tailored to their needs. He believes fashion exists to serve, not intimidate.

"I wanted a space that people could really explore and feel at home in," he says. "Most retail spaces are long and narrow and I think people can be quite intimidated by that; they feel on show and watched by store staff. I didn't want that, so my shop has lots of different corners so that hopefully people will feel welcome."

We'll see you at the checkout.

Self-Portrait, 49 Albemarle Street, London W1

From: AR Revista