“[I told them] that it’s not like Coachella, with girls in shorts and glitter on their faces,” she says. “I was desperate for it to rain to prove me right.”

The event gave Chung the chance to road test her favourite jumper from her new autumn collection, a baggy, colour-blocked top bearing the illustration of a face. Some of her autumn designs will soon be available at Lane Crawford in Hong Kong, and on her own e-commerce website.

Over a breakfast of coffee and scrambled eggs, I quickly get drawn into Alexa’s world of fashion, music and television. Her soft New York drawl, having lived in the city on and off for six years, is peppered with grime-music street jargon that she sometimes has to translate. She is clearly sharp, quick-witted and happiest when multitasking. “My brain works on multiple tracks, which is very annoying for my friends.”

‘Heels are to seduce men, bags to show off to other women’: designer Paula Cademartori

She’s also ahead of her time, in a sense. “Only this morning I sent a picture of the musician Lorde, wearing combat trousers, to my team telling them that I had been on the right track, and that [combat trousers] are coming in [to fashion]. But we had made some combats and they hadn’t sold well. We were too soon: it’s so annoying as I know they are about to pop off.”

Her fashion label debuted at the end of May with its summer collection and was an instant success. She lists her favourite pieces, but they have all sold out. She offers “see-now, buy-now” (items that are immediately available after shows) as she felt it was a “more democratic way of rolling it out rather than seeing a proliferation of items worn by celebrities before the collection is available”.

That summer collection relied heavily on the gut instinct of Chung, who has three times won the British Style Icon award at the British Fashion Awards and has 2.8 million followers on Instagram. However, for the catwalk show, stylist Cathy Kasterine presented a different perspective because, as Chung puts it, “I didn’t want to see a parade of fembots that looked like me.” The collection, though, is still clearly grounded in Chung’s personal style.

She is particularly proud of that first collection because “it was hustled together by a gaggle of strangers starting in a kitchen”. Now finishing work on her winter collection, she says the team is starting to cohere.

She has a Mulberry handbag named after her and in the past has worked on design collaborations with Madewell, AG Jeans (who, to Alexa’s surprise, actually expected her to lead the design team), and Marks & Spencer. In the end, she felt launching her own label was inevitable.

“It wasn’t a light bulb moment when sitting in bed one day in New York. I just thought now is the time,” she says, adding that it had been part of her game plan since the age of 16, when, as a model, she would design some of her clothes.

Surrounded by a strong support team, she says, “I suddenly became motivated to do it, but I think that has to do with age [she is 33] and tiring slightly of the floaty life in New York,” where she worked as a music and fashion television presenter.

Her team includes Edwin Bodson, formerly the head of atelier at Haider Ackermann, as her managing director, while her backer is Peter Dubens, co-founder of Oakley Capital Private Equity, who also invests in Bella Freud’s label.

Chung describes Dubens as a compelling character and recalls her rather unprepared pitch to him over a food tasting in his club. It took another year before all the pieces fell into place and she moved back to London to start the label (although she retains her flat in New York’s East Village).

Having no formal design training hasn’t made her nervous so much as frustrated. “I hate not being knowledgeable about something,” she says, adding that she initially found it difficult to communicate with her team about what she wanted. “It’s a bit like being a toddler when you want to have a grown-up conversation.” The learning curve, she explains, has been steep.

The best looks from Paris haute couture fashion week

Raised in the southern English county of Hampshire by her Chinese father, born in the East End of London, and mother, a Hampshire native, Chung was scouted to be a model at the age of 15. She focused mostly on commercials and the covers of teen magazines, and grew confident in front of television cameras.

She was hired to front a Sunday music show on British national television channel Channel 4 aimed at the mainstream teen demographic. She didn’t have a huge clothes budget, so she bought clothes from H&M, Zara and Topshop. The way she styled them got noticed and commented on by bloggers.

She describes her style as a balance in terms of silhouette and accessorising. For an event that evening she was planning on wearing an Emilia Wickstead dress and bumbag “so I don’t look too princessy”.

Just who is responsible for the fashion scene’s parka revival?

Her style also includes a large dose of irony. She thinks humour has a lot to do with style, so thought nothing of dressing like her mother in a Barbour jacket, piecrust blouse and loafers to go to a cool club and see rock band The Horrors play. “I thought everyone was in on the gag, but now it is less funny, as I am old,” she says.

Nowadays, that style is evolving. Her summer collection included tea dresses to wear to friends’ weddings (she was recently bridesmaid to Pixie Geldof at her wedding in Mallorca), trench coats and leather mini dresses. Autumn has frilly shirts, striped polo shirts and little gingham dresses. You can’t help but imagine Alexa wearing them all.