Marks and Spencer’s fortunes, revealed this week, continued the trend of recent years: if you can eat it, everybody loves it; if you can wear it, nobody wants it. Womenswear is the department that has struggled the most, although chief executive Marc Bolland declined to break down the current numbers in that much detail. But the store’s non-food sales are down 1.2 % in a retail world where even standing still is seen as going backwards.

I would advise M&S, before they get in any more consultants at eye-popping cost, to wait outside the store in Birmingham’s Pavilions in the hope of meeting Chris Marshall, 60. “Say, if pink’s fashionable, their pink is always the not-quite-right pink. I don’t know how, but they always get it just slightly wrong,” she says.

This, it strikes me like an arrow, has been true forever. It’s in Marks & Spencer DNA: the stripes are always a bit too wide, the jeans too forgiving, the sequins too bulky and mini skirts too long, but not long enough to be anything other than a mini skirt. “It’s ageing,” Marshall continues. “I’m 60, but I still look at M&S as not being trendy enough.”

“Also,” she continues archly, “I’m a size six. The selection in a size six is very limited.” Her husband, Clive, 62, is probably not a size six, but agrees: “I mainly wear jeans, and I don’t like them baggy.” He doesn’t like the Jeremy Clarkson look, confirms Chris.

The consensus is overwhelming: whoever these clothes are designed for, it is someone a little bit older than oneself. Rhiannon, who is 25, says: “I’ve been in here with my mother, who’s 54, and even she said, ‘I’d be dressing like my own mother’.”

Imelda, 61, and Pauline, 67, have both been in to buy a pair of jeggings, which they explain by making the international mime for elastication. “My daughter’s in her 30s, and she would never shop here,” Pauline says. But does she ever see anything you’re wearing and say you look nice, I ask. “Nope,” she says emphatically. “They’re trying to be a bit Monsoon-y now, I think,” says Imelda. “They’re all very loud prints. I wouldn’t wear them.”

Sheila, who is in her 70s, thinks Marks and Spencer is marvellous, but is the only fan: her friend, Sam, 45, says, “If I ever end up with any M&S clothes, it’s when I go to a charity shop.” “She could be my daughter,” says Sheila, “but we’re actually just good friends.” Maybe that points towards M&S’s problem: their clothes haven’t got older, old people have got younger.

But the issue runs deeper than that. Roger Waters, 68 (“Since I’ve stopped playing in Pink Floyd, I don’t get a chance to shop there so much,” he starts) claims to buy very little from the shop but then, it turns out, is dressed almost head to toe in Blue Harbour (M&S’s “British sports-inspired collection”). “Years ago, they were renowned for quality. And now they’re trying to compete with the rest of the high street.”

His wife, Anita, 68, chimes in, “I used to buy these trousers, but now they’ve made them cheaper and they’re not as good.” She shows me the old-variant trouser. They look as though they’re going to last her another 15 to 18 years. It’s tough being the purveyor of quality in a disposable world.

Men are slightly keener on the store: David, 38, thinks it’s a reasonable place for a person his age to shop, has a couple of M&S suits and is in to buy a shirt for his father. “At the smarter end of the spectrum, it’s fine,” he says equably. Philip, 47, is perfectly happy to buy his socks in Marks. As for the rest of his wardrobe, “I tend to wait for people to clothe me.”

Nowhere across its four floors does the Birmingham shop submit to the principles of modern store-craft: the bra at the front is always the largest not the smallest; the lighting is sensible not flattering; there’s plenty of everything for everyone with none of the wholly simulated sense of urgency you’d get in Zara; slim but recognisably human-shaped mannequins model unchallenging outfits that could withstand inclement weather.

A lot of these looks, frankly, appear more like camouflage than clothes, shape-hiding garments that would allow the cunning partygoer to blend in with other wearers of Marks and Spencer. It is a sensible place where sensible people can buy things that they need. So is the problem with M&S or Britain’s shoppers? Arguably, not the store – but we’re the shoppers they’re stuck with.