From skinny to barrel and ultra-high to low-slung, jeans trends are ever changing – so how can we choose the perfect pair for us, and maintain them properly?

Few items of clothing are both as iconic and ubiquitous as a pair of jeans. With era-defining silhouettes that capture cultural moments in time, jeans are a wardrobe staple. But they're also one of fashion's most polluting categories, prone to high trend cycles and – as a result – hanging in our wardrobes unworn.

Take this season's trends. Last year, Vogue reported that skinny jeans were making a comeback, only to call it a fleeting moment 12 months later, and now they’re back again – with the Princess of Wales as poster girl. "Slim" silhouettes are in, too, alongside belted and baggy, and – the shape of the season – barrel-leg jeans: a fitted waist that leads into a slightly voluminous leg and then tapers at the ankle. With as many fits and trends as there are body shapes and tastes, how do we invest in the perfect pair?

Personal stylist Alexandra Fullerton says that the barrel-leg silhouette works with most body shapes. "They are pleasingly loose across the legs and sit around the true waist, therefore they should have a lasting place in one's wardrobe," she tells the BBC. "They are just a baby step away from the boyfriend jean, which is now a perma-trend."

But Fullerton stresses that buying a pair of jeans should be a marathon, not a sprint, and advises her clients to build a shortlist of styles based on research. What washes do you like? Which brands do you admire? Who in the public eye has a similar body shape that you can take tips from?

"Putting in some work – that's a couple of hours in a real-life store with a well-lit fitting room and ideally a friend – will ensure the best purchase," says Fullerton. "Department stores with dedicated denim shops are the best place to start. Whatever your budget, jeans should be an investment so shop with longevity, rather than trends, in mind."

Fullerton cautions that extremes – skinny and super-wide or ultra-high and low-rises – are more prone to cycling in and out of fashion. "Better to choose a less severe silhouette that will outlast any fad, like a straight leg or modestly wide jean with a mid-to-high rise which will be classic for years ahead," she advises. "Mid-blue is always the best option for washes."

No jean has stood the test of time quite like the Levi's 501. Patented in 1873 by Levi Strauss and Jacob David in the US, it was originally created as durable, hard-wearing 100% cotton overalls for miners and farmers. But in the early 1950s, blue jeans came to signify youth rebellion, after both Marlon Brando and James Dean wore Levi's 501s in The Wild One and Rebel Without a Cause. And who can forget Susan Sarandon and Geena Davis denim-clad in high-waisted jeans for Thelma & Louise in 1991.

"When Japanese selvedge denim replaced the ultra-baggy, hip-hop fits of the mid-to-late-90s, and then Levi's launched its Red collection of twisted, ergonomic jeans, the denim landscape changed forever," says denim designer, lecturer and historian Mohsin Sajid. "From then, denim became more elevated, appearing on catwalks and in designer brands'........

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