The key fashion pieces right now? Clothes you’ll want to still wear (or sell on) in five years’ time | Jess Cartner-Morley

I suppose, in theory, sustainable fashion shouldn’t have any one look. After all, surely the whole point of prioritising ethics over aesthetics is that clothes design should not be all about what they look like, but about how they are made: the raw materials used, the industrial processes undergone, the people employed, the carbon footprint of transportation. But in reality, it does have a look. You can’t take aesthetics out of fashion. Sustainable fashion has style rules, too. Just different ones.

Some of this is simple practicalities. Sequins, being mostly made from non-biodegradable fabrics, are a no-no on environmental grounds. If you jazz up a T-shirt with decorative zips or emblazon it with beading or glued-on trims, you make it much more difficult for the fabric to be usefully recycled or reused. Therefore, streamlined design is favoured. Textile dyeing is one of the most water-intensive elements of the clothes production cycle, so bright colours can be a red flag.

A lot of baggage has been layered on to our idea of what sustainable fashion looks like: nubbly, coarse fabrics that seem more homespun, less industrial, than shiny ones, whether they are or not; bamboo, birds, waves and other prints and patterns that celebrate nature; loose silhouettes, to avoid semaphoring personal vanity; raw edges and textures to renounce problematic levels of bling.

But this is changing. With circularity now a cornerstone of mainstream strategies toward sustainability, consumers and brands are looking at clothes through a new lens. Circularity is focusing attention on the longevity of a garment’s appeal and its value in the future resale market. This is a radical departure for the value system of an industry that has historically hero-worshipped brand new clothes – preferably with tags on, and tissue-wrapped – and has tended to dismiss as irrelevant to the fashion conversation any clothes that have already been worn.

A 10-year programme for industrial change, to which the government has pledged £80m in funding, is focused on “creating a world-leading circular fashion ecosystem in the UK”, according to the British Fashion Council (BFC). At the Downing Street announcement of the scheme, Stephanie Phair, the chair of the BFC, set out a vision of “a city like Leeds, which has a rich history in manufacturing and textiles, retaining its role as a key part of the fashion and textiles industry, and an example of a circular city with reprocessing plants and energised high streets with takeback schemes”.

Meanwhile, Love Island set the tone for a resale-powered summer with sponsorship by eBay as outfit provider for the series, and Dr Martens partnered with the fashion app Depop to provide a sales platform for refurbished footwear. With the resale market reportedly growing 11 times faster than traditional retail, according to a global report conducted by Thredup, brands including Valentino and Gucci are looking to partner with customers who have past-season pieces in their wardrobes through validated buy-back schemes.

Circularity is far from a magic bullet for the fashion industry’s environmental woes; rental firms have faced criticism for the impact of transportation and cleaning involved when a dress is whisked from one wearer to another every few days. But the most fundamental issue with circularity, from a sustainability point of view, is both its biggest flaw and its biggest asset: namely that circularity does not attempt to stop fashion consumers shopping. Faced with the scale of the climate emergency, many campaigners believe any policy that panders to our desire to shop feeds the problem. But others maintain that by providing a scratch for the itch to shop, circularity offers a roadmap that consumers and brands can realistically be persuaded to follow.

While the environmental impact of fashion’s new focus on preworn clothes may be less than transparent, the impact on how we want to dress is clear. It is also dramatically different from the stereotypes that have lingered around ethical fashion. The most desirable clothes now are those that will still look desirable in five years’ time. That means dresses in black and white, rather than in whatever the colour of the season may be.

In other words, the most radical statement you can make with your outfit is to signal that you have chosen it not according to the whim of the fashion moment, but rather with a view to ensuring it will have a long and hardworking life, in your wardrobe or someone else’s.

This week, the September issues of glossy magazines arrive on newsstands, with their big reveal of the season’s new look. The key pieces for the coming autumn? White cotton shirts, tailored trousersuits, knitted sweater dresses, black biker boots, tan leather belts and gold chain necklaces. Trends are so last season; timelessness is hot right now.

Ralph Lauren, which has built a luxury empire not on setting trends but on a hold-steady vision of timeless Manhattan style, is one of a number of establishment brands that now find themselves at the leading edge of fashion. Its 1980s preppy classics and 1990s proto-streetwear are highly prized by the Generation Z consumers who have made the brand one of the most searched-for names in preloved fashion. Devon Leahy, the head of sustainability at Ralph Lauren, recently told Vogue Business that “timeless design” was key to sustainability, because of its power to future-proof the desirability of clothes being made. Leahy sees a scaling up of circularity, which is likely to include brands taking a percentage of resale profits in exchange for authentication, as an important step towards separating the financial growth businesses still rely on from the heavy carbon footprint of producing new clothes.

The most ahead-of-the-curve fashion of the moment does not look radical at all. Establishment classics are the new avant garde, because the aspirational image most aligned with the zeitgeist is the one that doesn’t follow a trend cycle. From jeans and sturdy biker boots to striped cotton shirts and simple tailoring, from cotton sundresses to gabardine raincoats, the timeless is back in the hot seat. The new look? Old-school classics, played on repeat.