Forget sliders, dad sandals, Crocs and even Birkenstocks. To get ahead on summer 2019 fashion, the footwear to buy into is the humble flip-flop. The thonged sandal – which dates back to at least 4000BC – is, of course, a regular sight from beach to city street every summer. But it hasn’t been properly fashionable, arguably, since the early 00s, when women like Paris Hilton, Nicole Richie and Mary-Kate and Ashley Olsen made it as integral to their LA around-town look as XXXL sunglasses and four-figure handbags worn hooked over one arm.

With this era rediscovered by a generation of people who were children around the turn of the millennium, it makes sense that flip-flops are in focus again. They were a trend among influencers at Copenhagen fashion week this year – increasingly a site for emerging street style.

Designers from Michael Kors to Molly Goddard featured versions of flip-flops on the catwalk for spring. The Olsen sisters, meanwhile, have consistently worn them. When a photograph of the duo for WSJ magazine was shared on Instagram in August to announce the addition of menswear to their fashion line The Row, it was the black flip-flops they were wearing that caused a frenzy. The post has so far received more than 10,000 likes.

Michael Kors’ take on the flip-flop for SS19. Photograph: JP Yim/Getty Images for Michael Kors

Part of the appeal of the flip-flop is, of course, the price. The biggest brand in the world of flip-flops is Havaianas, which was founded in Brazil in 1962. With countless variations available, the Tradicional style is £16.

Flip-flops on the catwalk at Molly Goddard, SS19. Photograph: Niklas Halle’n/AFP/Getty Images

Retailers including Net-a-Porter and Asos are tipping the flip-flop as the style for summer 2019. “Flip-flops are a big deal for Asos for spring,” says Aisling McKeefry, Asos head of design. “Originally evolving from Instagram, the trend is for simple toe thong designs on to flats and super-sexy glam heels. Toe loops are also going to be trending.”

Elizabeth von der Goltz, global buying director at Net-a-Porter, agrees, saying: “For spring/summer 19, Staud are doing this trend particularly well with their chic asymmetric styles in a variety of textured and leather colourways. Chloé too have amazing wrap versions. We’re excited to have bought heavily into these collections for next season.”

Pernille Teisbaek wearing flip-flops in Paris, July 2018. Photograph: Christian Vierig/Getty Images

The stylist Jeanette Friis Madsen, a street-style favourite who was photographed in flip-flops at Copenhagen fashion week, believes their relatability means they are a sure thing for the summer. “They’re easy, affordable, comfortable, casual and fun,” she says. Rather than saving flip-flops for the beach, she advises using them as a way to bring a casual edge to daytime outfits. “They’re perfect to downgrade a flashy summery dress,” she says. “Or mix them up with a pair of wide suit trousers for an effortless expression.”