Comparisons to American fashion favourite Olivia Palermo would not be unfair: both have reality television to thank for their fame, although both seem keen to leave that reputation behind; both boast an elevated girl-next-door beauty, all honey limbs, glossy hair and sweet smile; both possess a certain froideur that, when teamed with their slim figure and pretty face, make them perfect brand ambassadors - a blank canvas on which labels can project as they wish. But a more accurate comparison would be with Jessica Simpson. Perhaps not similar in look or personality to the understated and relatively reserved Mackintosh, self-made billionaire Simpson is certainly the one whose path she is following in terms of under-the-radar fashion power. Harnessing the social-media sway that she has, proven by her ability to sell products for other brands, Mackintosh has an ability to directly impact sales of her own collection in a way that other designers cannot - as one London-based name, who would prefer to remain anonymous, attests.
"Celebrity endorsement has been key to launching our brand," the designer - who has also dressed stars including Kendall Jenner, Cara Delevingne, Poppy Delevingne, Olivia Palermo, Rita Ora and more - told us. "Millie was one of the first girls to wear our pieces and the sell-through that she generated was astonishing, it was incomparable. Her fans are dedicated to emulating her style and following her fashion advice."
Her Instagram feed oscillates between serious beauty selfies, food pictures, gymstagrams (a favourite of the Daily Mail) and pictures promoting her own collection. So far, so easy, you might think. Mackintosh is pretty, privileged and can catapult a poorly performing style to a best-seller with just one Instagram post - but the entrepreneur has no intention of resting on her laurels.
Labels collaborating with celebrities is nothing new - everyone from Kate Moss to Gigi Hadid and David Beckham has lent their name to one - but Mackintosh's collections differ in key ways. Firstly, they are independently produced by Mackintosh and her team, then sold via her website and ASOS - a more challenging proposition than solely using an older label's existing supply chain, but with a greater possibility of control. Secondly, the clothes are designed by Mackintosh from scratch and are not an adapted edit chosen from a particular store's archive - in the way that, say, Alexa Chung's new collection for Marks & Spencer is. Mackintosh is involved in the collection from conception to completion.
"It's incredibly important to me that I am involved in every aspect of the collection," she told us. "Moodboards are my foundation and starting point for each season and I've become a little obsessed with Pinterest. It's a great source for inspiration and I can check in on it on my phone when I'm running around. After moodboards have been streamlined, the design of each piece is then sketched out. Usually there would be three or four different variation sketches for each piece, to ensure that proportions work and we are creating something that is not only fashionable, but wearable. Once designs are approved we then move forward with selecting fabrics and edit down to the final collection pieces, which are then transformed into samples. There are times when samples are not quite what we envisioned, so we try to re-work them when fitting to a model. Sometimes things just don't work and I would rather drop the option than produce something that isn't going to be the best that it can be."
Clearly a perfectionist, Mackintosh's process seems no different to designers such as Victoria Beckham who fit and improve each sample personally, without ever pretending to be the one sketching or cutting. But although aspects of the design process see her turn to her production team for advice on their areas of expertise, one place that she loves to be fully involved is when the sales process begins.
"Once samples are signed off we then reach out to buyers and our already partnering stockists to gauge what pieces work for them, their audience and gauge feedback on anything that may need tweaking," she explained. "I find buying meetings a very exciting environment, although having industry eyes critiquing your designs is nerve wracking, there is an element that is totally electrifying. With the backend completed we then enter the world of shooting all looks ready for e-commerce, PR and sales; which I really enjoy. Product push-out tends to be every four weeks online, so we have continual releases, maintain market presence and traction all year round."
Mackintosh's thrill at seeing her collection worn on the street of course extends to celebrity fans as well, and like every brand she has a wish list of stars who she would love to see sporting her pieces. Coincidentally, or perhaps appropriately, her top three targets all have fashion lines of their own.
"Gigi Hadid has got such a great body and look, I'd love to see her wearing the collection," she confessed of the Vogue cover girl who recently lent her name to a Tommy Hilfiger collection. "My big style crushes are Rosie Huntington-Whiteley and Olivia Palermo. They all have such great style and are free in their individuality, and mix in the boho look that I really love. Mostly, I design for my friends, my sister, sometimes my mum, the girl next door; for the girl I used to be and the woman I want to be. I want my designs to be accessible and inviting for anyone and everyone. I like to have a real mix, my personal style changes day to day, which is a definite reflection of what I create and that's why I wear every piece. Variation is luxury, because we can be something different every day if we choose. Isn't that what fashion is about?"