Almost a week on from the Super Bowl, Kendrick Lamar’s half-time performance is still being talked about. In particular, the pair of boot-cut jeans worn by the American rapper as he commanded the stage. But while those came from the luxury fashion brand Celine and cost £830, the scores of backup dancers surrounding him wore a high street label – to be precise, £19.90 oversized T-shirts and long-sleeved tops from Uniqlo.

It is another big coup for the Japanese-founded retailer that has steadily grown its presence on the British high street with 20 stores and counting. For a brand previously seen as a little boring, all beige and greige logoless casual wear, it is quite the vibe shift. It now infiltrates the wardrobes of everyone from gen Z youngsters who love its cargo joggers and cult crossbody bag, to their grandparents who rave about its Heattech thermals and affordable cashmere jumpers.

Now it has its sights set on winning over the fashion world. Last September, Uniqlo cemented its status as a serious player when Clare Waight Keller became its creative director. The British designer previously held stints at Calvin Klein and Chloé and during her three years as artistic director at the French fashion house Givenchy designed the Duchess of Sussex’s wedding dress. The fact that a high street retailer had persuaded one of luxury’s most influential fashion designers to decamp from a world of catwalk shows and celebrity-fronted campaigns speaks volumes about Uniqlo’s sway. It also points to a changing definition of what luxury means.

Waight Keller says part of the lure of Uniqlo is that it appeals to everyone. “We have to remember there are a lot of people who don’t have a lot of money. As much as they aspire to buy luxury, it’s not realistic for everyone to afford it. I have a mission in me to bring the quality of design that you would get from luxury to a broader audience. I think everybody deserves to wear something beautiful.”

Uniqlo’s appeal has not always been so widespread in the UK. Founded in Hiroshima in 1984, it ended up closing 16 of its stores within 18 months of first launching on the British high street in 2001 due to poor footfall.

Although it has tried to distance itself from fast fashion claiming it does not chase trends and offering in-store repair and recycling, Uniqlo still produces a staggering 60m items annually. On the ethical fashion Good On You app it scores a “it’s a start” – the same rating as H&M.

Two decades after its UK launch, Uniqlo has found its stride. Its £69.90 down jackets are a fraction of the cost of a £360 North Face puffer while its limited-edition collaborations with designers including Loewe’s Jonathan Anderson sell out within minutes. Joy Montgomery, the commerce editor at British Vogue, says the fact it “delivers on form and function without breaking the bank” sets it apart from other high street stores. “Sometimes we just want a staple that comes in five colourways and has a handy pocket for our AirPods.”

Nearly six months into her creative director role, which includes overseeing Uniqlo’s mainline and Uniqlo:C, a capsule collection of elevated pieces, the Waight Keller effect is beginning to trickle down into stores. She has expanded the colour palette by introducing sharp citrus shades and romantic pinks to its cashmere and linen ranges.

Timelessness is important. The T-shirts worn by Lamar’s dancers launched seven years ago. Waight Keller still wears clothes she bought from the brand 15 years ago. To maintain relevancy she is focused on proportions and fine-tuning silhouettes. A “track suit” consists of trackpants and a blazer. Tops and dresses come with in-built bras while shorter skirts include built-in shorts. Waight Keller is particularly pleased with a crepe jersey dress with spaghetti straps and a cutout back detail that does not require a bra.

“In the summer women can feel uncomfortable in the heat,” Waight Keller says. “I wanted to eliminate that. You don’t need to find things that work together. You can just put one thing on.” It is this type of pragmatic approach that is sure to win over fashion shoppers lamenting the lack of female-led luxury houses. As for It bags, following the success of her pocketed tote bag that can fit a laptop and sold out in 10 minutes upon launch, there is another £24.90 version on its way with even more pockets.

This function-first approach partly comes from Waight Keller’s inspiration – people-watching at airports. “There is no fixed demographic. So functionality and simplicity are key. There is a purist approach that is rooted in Japanese culture. Everything has a reason. There is nothing superfluous.”

Uniqlo essentials

Round mini shoulder bag, £14.90
Deceptively small looking, this can fit everything from your phone to a rotisserie chicken.

Cotton crew neck T-shirt, £19.90
Features a special AIRism fabric to keep wearers, including Super Bowl dancers, cool.