“I want something in my wardrobe I can wear in two years’ time,” says Kate Bostock, executive director for clothing at Marks & Spencer. Don’t we all. Let’s face it, we’re bored with designer copies, our feet are blistered from £3 plastic shoes and we’re increasingly aware of the ethical ramifications of sweatshop separates. And so is one of the most influential women on the high street.

Bostock, the equivalent of a prophet in the fashion Holy Land, admits her own wardrobe is undergoing a seismic shift. “Beautiful fabrics and detail are more important to me now than the fast fashion of two years ago.” Watch out: this means it’s only a matter of time before we all feel the tidal force of a sartorial sea change on the high street.

Gone is the attraction to quick and cheap fashion, says the woman tipped for the top when Sir Stuart Rose steps down. And quite right, too. Can you envisage the 50-year-old female buying director in front of the board, wearing a body-conscious designer knock-off, perspiring through a thin layer of scratchy synthetic fabric, and hobbling in £5 Primark pumps? It’s worse than imagining Jeremy Paxman in his underpants. Well, almost.

Investment dressing, the knight in shining armour on the retail horizon, is an attractive style proposition that sits comfortably in the current economic framework. Buying timeless and well-made clothes is tantalising after half a decade of high-speed, low-quality turnover. Yes, women are feeling the effects of the credit crunch, but an economic downturn has a comparatively small effect on the act of shopping. Women will shop even if the world threatens to explode on entering a changing room. It’s just how they shop that differs.

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Marks & Spencer commands 12 per cent of the womenswear market in the UK, making it a microcosm of the wider consumer picture. According to Bostock, shopping habits really are changing: “M&S customers are more discerning than ever. Clearly, they are very conscious of budgets. It is important that when they are shopping they find something that excites them, that makes them feel they have to have it. Equally, customers are asking more and more for wardrobe staples, for quality they can invest in. That has been quite a step change, and it moves very much into the M&S territory.”

A sense of relief is discernible in Bostock’s voice. Finally, a change in shopping habits that suits the volatile behemoth of the British retail sector, and a new in-store collection, Autograph Essentials, that meets these demands. Given the recent slump in M&S sales, a range that appeals to the faithful and draws in a new discerning customer is a glimmer of light in an unpredictable future.

Bostock puts Autograph Essentials into the “buying less and investing better” bracket. It includes the classic white shirt, trouser suits, shift dresses and a trench coat: a core uniform made of long-lasting, luxurious fabrics that defies the whims of trends.

Luxury has not always been synonymous with M&S; in the past it has been criticised for the overuse of synthetic fabrics and poor fit, but here marks the change. “We have introduced new suppliers that are typically making top designer collections,” says Bostock. Hold on a minute. Suppliers who manufacture for designers? Now you’re talking. “All our customers know that luxury fabrics cost more. Our ladies are happy to pay for it, they told us. They said, don’t give me the synthetic blends, give me the real thing.”

So how much will they pay, and does the Essentials collection feel markedly different from other ranges? Prices range from £45 for a shirt and £50 for a dress, up to £169 for a trouser suit. The cut of the trousers is flattering on the bottom (the key litmus test), a ruffle-front shirt feels more Reiss than conventional M&S, and the suit jackets have the all-important nipped-in waist that pull them out of Matalan territory and more towards McQueen. It is unashamedly more sophisticated than most of the other ranges in store.

What comes as the biggest surprise is Bostock’s honesty about the timing. Credit crunch plus wardrobe essentials equals perfect strategic planning, right? Wrong. “If I am honest, it’s coincidental. The evolving high street is driven by the customer; this is the way the customers were feeling. Slightly by accident it seems to have landed at the right time. But I suppose that’s because we have worked together on it and recognised what people are looking for.”

Bostock can thank her focus groups for the tip-off (M&S has customer feedback groups situated across the country), and the high street would do worse than to follow suit. Shoppers want quality essentials, and they are prepared to invest in them. Who better to offer advice? After all, isn’t the customer always right? Fortunately for Marks & Spencer, Kate Bostock already knows this.

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