Isaac Mizrahi's latest collection pays tribute to grown-up ladies.
Meet Isaac Miz-rahi's muse, meet his mother. The designer muse is usually willowy, sinewy and doesn't talk back. Sarah Mizrahi, "Noo Yawk Mom" extraordinaire, is short, round and chatty.

She was sitting up front at Isaac Mizrahi's New York show last week, in one of the "star" seats usually reserved for Julia Ormond or Julia Roberts. And metaphorically, she was up on the catwalk, too. The man who admits that, as a boy, he would sneak into his mother's bedroom to steal money to buy trimmings, now pillages her wardrobe wholesale. Up on his catwalk were stiff duchess satin gowns, cocktail dresses overlaid with caramel lace, bold floral summer dresses and overblown pearl-encrusted party frocks - every last one of them a tribute to mother love, (except for the ones that looked like a tribute to Queen Mother love).

Isaac Mizrahi is not alone in this. Such is the adoration between Lucienne Saint Laurent and her son that she has tears in her eyes at every one of his shows - and with four ready-to-wear and two Haute Couture shows a year for over 30 years, that's a lot of tears. Bad boy Alexander McQueen seats his mother and his auntie centre front for a bird's-eye view of the rear cleavages and bare breasts of his oeuvre. Vivienne Westwood's mother, Dora, is so much a part of the Westwood team that she travels to her daughter's Paris shows in the back of the team minibus, sewing up last-minute frocks as she goes. But Isaac Mizrahi loves his mother so much that he wants Linda Evangelista, Naomi Campbell and Amber Valletta to dress like Sarah Mizrahi in her heyday (or at least, how Isaac and Sarah wish she could have afforded to dress).

Things have changed on Planet Fashion, where, for so long, the only thing to worship was youth. It is no longer an ageist insult but rather the greatest of compliments to say that someone looks like their mother. Grown- up "lady" clothes, stark and starched dresses, to-the-knee coats over matching to-the-knee dresses are what the most happening of groovy young women now want to wear - improbable as that might sound to those who wore them last time around. Audrey Hepburn, Grace Kelly and Jackie Kennedy are, as always, the most oft-cited inspirations. But give a teenage catwalk queen a bit of backcombing, a smear of obvious eyeshadow and a frock that rustles as she walks and she's much more likely to resemble someone in her own family album (although, given the youth of these girls, it's as likely to be granny as mummy.)

In Europe, where grown-up lady dressing has emerged as the big fashion trend, you can probably thank Miuccia Prada of Milan for re-introducing stiff elegance. A few seasons back, the accomplished stylist, who employs a team of designers to work on her family's Prada line, just couldn't help herself from rehashing the clothes she recalled from her stylish Mama's wardrobe. Now, in Paris, in London and elsewhere in Milan, Miuccia's stiff tailoring and stand-up-by-themselves cocktail frocks have had a huge influence.

But Isaac doesn't need the inspiration of Miuccia's Italian Mama. He has his own New York Jewish mother to inspire him. Included in his collection last week was a pair of sandals with huge daisies up front. When he was a little boy, Isaac Mizrahi's mother spruced up a pair of mules by sewing daisies on to them "and who knew he was looking. He was four years old and he noticed the daisies on the mules ..." says an amazed Sarah.

Mizrahi is fearless in the face of the "Mother of the Bride" occasion wear, the kind until recently stocked only in those lady shops that are too terrifying to enter. But lady clothes fit and flatter, and that isn't such a bad idea. Given the choice in New York last week, what would you have wanted? A perky stiff black satin cocktail dress, sliced over pink net and with a black satin bow bang on the breast bone or a to-the-ankle shirt dress in clingy jersey the colour of custard? (The latter by Calvin Klein, the former by Mizrahi). Would you have preferred a white, Velcro- fastening tunic and matching tight trousers (the dental orderly look, as offered by Miu Miu)? A pair of skin-tight, white trousers and a stole looking like a bath towel as offered by Donna Karan? A brightly coloured sheath dress to make you resemble a Caran d'Ache pencil by Ralph Lauren? Or something joyfully whipped up from Angel Delight chiffon by Isaac Mizrahi?

The Mizrahi offering was certainly the most peppy and fun in an otherwise dull New York where everyone had a shirtwaister, a pair of hipster trousers and a skinny Seventies-style shirt on offer. Isaac's Mummy clothes offered a rare moment of tender loving design amidst a sea of cynical design-by- numbers clothes, often in murky unflattering colours. But Mummy clothes were not the only reason the designer with cartoon 3D hair hurled himself gleefully down his own runway as if he were auditioning for Disney-on- ice. Isaac Mizrahi is in fine form because he is also a movie star.

An all-singing, all-dancing Mizrahi plays the leading role - himself - in a movie called Unzipped that co-stars a fiendishly snappy Linda Evangelista plus Naomi Campbell and her navel ring. Oh, and Sarah Mizrahi. Unzipped has already taken a respectable $2.7m at the US box office (not bad for a 70-minute, mostly black and white documentary about an extremely out gay frockmeister whose greatest private revelation is that he adores Mary Tyler Moore). Unzipped will be screened as part of the London Film Festival next Monday, 13 November.

Mizrahi emerges as a star, one who can do great Eartha Kit impressions and beret-hurling Tyler Moore impressions

Because of Mizrahi's joie de vivre and because of the co-starring role of his mother, to whom he is attached by telephone as if by umbilical cord, Unzipped works where no fashion movie since Funny Face has worked before. Without needing a Robert Altman-sized production, Unzipped affectionately reveals much about the hard graft and the lunacy of a world where no one thinks it is bizarre that an aged fashion editor approaches a fake fur jacket and talks to it - "Hello! This says hello to me very clearly".

Others have tried to reach similar revelations about the world of fashion, but have ended up committing its only unforgivable sin - boring the audience.

Unzipped, by contrast, is an affectionate portrait of a silly world, made by Mizrahi's then boyfriend, Douglas Keeve. As yet, neither Isaac nor Sarah have further movie plans. Their mutual first love is frocks. At one point Isaac admits he is all out of ideas to a horrified Sarah. "You haven't got any ideas! Why don't you let me look [at what you are doing] Isaac ... Excuse me, that's not funny at all, I have a very good eye, honey."

No one would be surprised to learn that she cast an eye over the just revealed spring/summer 1996 collection.