Size, age and colour are no longer a barrier to a career on the catwalk – that was the message from London Fashion Week. Fashion editor Susannah Frankel reports

Muscular athletes in Stella McCartney's sportswear line for Adidas, Christopher Kane's blonde bombshells, models well into their thirties at Giles Deacon, a little ethnic diversity across the board ... One could be forgiven for thinking that fashion had developed a conscience, if this week's London collections were anything to go by.

The reasoning behind such a move is as likely to be commercial and aesthetic as it is ethical – fashion is famed for a ludicrously short attention span, after all – but the fact remains that designers are increasingly hiring a wider variety of models and it is likely that this will continue next week in Milan and straight after in Paris.

Not many people working outside the fashion industry will recognise the name Russell Marsh, but as the casting agent behind many of the world's most high-profile advertising campaigns, glossy magazine editorials and catwalk shows, he is extremely influential.

On Wednesday he told The London Fashion Week Daily, a free news sheet funded by the British Fashion Council: "I like reality, especially in times like these. We need a wake-up call. I think it's time people saw things for how they are. Grow old gracefully, I say."

Given that, for years, Marsh has been at the forefront of a mindset decreeing that seeking out the youngest waifs in the world to model is the last word in high style, this seems like quite a radical about-turn. In particular, Marsh works for Prada, whose catwalk famously launches the careers of a fresh crop of models every season. Because of this, the more established names (and established can mean a model who has worked for six months or, if she's lucky, two or three years) have become almost as disposable as the clothes they wear. But that, may be about to change.

"The models need to be athletic, confident, powerful," Marsh continued, putting his money where his mouth is by casting Lara Stone – who is positively pneumatic by fashion standards – to open Christopher Kane's show on Tuesday. "Lara is everything you want," Marsh said. "She's slightly bigger than the other girls and on the runway that really makes a statement."

Marsh made a not entirely dissimilar "statement" when he cast Jourdan Dunn, an 18-year-old British-born model, for Prada's previous show six months ago: she was the first black model employed by this designer since a young Naomi Campbell. Dunn has appeared in every heavyweight fashion and style magazine and stars in Topshop's current advertising campaign. "I think the look of the models is definitely changing," said Sarah Mower, a contributing editor to the American Vogue website, reporting from London this week. "Fashion is always changing and people are just really bored by that characterless, Caucasian look. Neither is it demonstrable that it sells clothes any more.

"Because of the economic climate, designers are perhaps more aware of their customer now than they have been: she's got money, she's over 35 and she wants to see people like herself as opposed to women half her size and age."

Mower cited the July issue of Italian Vogue, which famously featured only black models, as having raised awareness about expressing racial diversity. "That really moved things on," she said. "Now we have Alek Wek, Sessillee Lopez, Jourdan Dunn. We know their names and their faces are instantly recognisable. Fashion is a soap opera and we want to know who these women are."

The halcyon days of the supermodel are gone, but she is still in demand. Linda Evangelista is the current face of Prada and Claudia Schiffer has returned to represent Chanel. Campbell fronts the latest Yves Saint Laurent advertising campaign.

The designer Giles Deacon brought back Emma Balfour, who rose to prominence alongside Kate Moss but has since retired, Liberty Ross, who appeared not long after, and Christina Kruze to model in his show. Deacon said backstage: "Christina Kruze is 39. She's the same age as me. I think those women are just as beautiful as any eighteen-year-old."

Until recently, the major shows and campaigns "have featured girls who may be no more than sixteen, who are generally white and whose career is very short," said Cathy Edwards, the fashion director of Another Magazine, the biannual edited and published by Jefferson Hack. "It's not just about that any more, though. There's much more variety. There are more black models and you only have to look at the current campaigns to see that designers are using older models too, models who people recognise and respond to on an emotional level. It's much easier to make a connection with those women and that is definitely a good thing."

Edwards, who also styled Emma Cook's show, said good health and natural beauty, as opposed to a younger, more waif-like aesthetic, were her criteria. "Clothes are always going to look good on skinny people," she continued. "Models are like other-worldly creatures, they don't look like the rest of us but we wanted ours to be aspirational, to look healthy and to have a good colour. There's a big difference between a woman who is born that way and someone who has to starve herself to fit the mould."

Erin O'Connor, herself successful on runways and billboards, is more aware of this fact than most. Today she vice-chairs the British Fashion Council, is vice-president of London Fashion Week and is founder of the Model Health Sanctuary, a refuge for models working at London Fashion Week where they can eat well, rest in between shows and benefit from relaxation therapy and even counselling, should they need it.

"When I started out it was very different," O'Connor said. "We had a longer period of time to cultivate our careers and enjoy the moment. Fashion is all about a search for newness and often today new means young." She agreed, however, that the difference this week was remarkable. "You can actually see the girls gaining confidence, literally finding their feet." She also attributes the changing environment to the model-of-the-moment, Agyness Deyn, who with her peroxide blonde crop, determinedly individual wardrobe and idiosyncratic good looks leads the new individuality. "I think Agyness represents something really healthy," O'Connor argued. "Because her look and personality is so strong, the designers work with her, it is a collaborative process, she has a certain amount of power."

She concluded: "Over the past year the look of the catwalk has been overwhelmingly positive, but we have to keep going with this. It would be wrong to say that all the problems have been solved because I've seen how young and vulnerable some of the models still are. It's going to be a constant challenge ... and it is up to all of us in the industry to take responsibility for that."

Catwalk highlights

Best show

Giles Deacon: Couture polish meets pop culture. Sculpted 60s shapes were combined with 90s minimalism, sporty, techno fabrics and metallic hats inspired by Pac Man, designed by Stephen Jones.

Most star-studded front row

Vivienne Westwood: Guests included Kate Moss, Pamela Anderson and Dita von Teese

Most royal front row

Issa: Included princesses Beatrice and Eugenie, and Charlotte Casiraghi, daughter of Caroline of Monaco.

Best model moments

Naomi Campbell and Jourdan Dunn closing the Issa show hand in hand with the designer; Emma Balfour at Giles; Cilla Black, left, in top hat and tails at Fashion for Relief.

Most 'resistance is useless' trends

Jumpsuits, playsuits (including all-in-one knickerbockers at Henry Holland), crop tops, cropped leggings, 80s headbands à la Bananarama (Danielle Scutt and Topshop), distressed denim (Meadham Kirchoff and Henry Holland) and snow-washed denim (Topshop).

Most striking colour combination

Pink (particularly guava) and orange, as seen at Richard Nicoll and Sinha Stanic.

Best dressed

Roisin Murphy:For her multiple outfit changes and genuine originality; for example, a pork pie hat worn with a white dress and shaggy fur.

Most imaginatively dressed guest

Kabir:The stylist was a one-man fashion show. Outfits included a grey feathered wig, emerald green suit and furry bear suit with drawn-on whiskers.

Best muse

Peter Jenson based his show on Jodie Foster's film costumes, from Freaky Friday (1976) to Silence of the Lambs (1991).

Carola Long, Deputy Fashion Editor