Her career spanned four decades; from the war years, when her red, white and blue dresses forced her to flee the Nazis, until the late Eighties, when the ready-to-wear trade finally put paid to it. But the accolade most frequently bestowed upon her designs by her clientele is "timeless".
She was a shy, secretive figure, only 5ft tall, who remained an enigma until her death in 1993, aged 90. Next week a private collection of 100 of her designs, mostly evening dresses, is to be auctioned by Christie's. Their breathtakingly simple lines stand as a rebuke to the constant change of the fashion industry: other designers sought change, she sought the constant.
Her designs transcend fashion. There are few garments in the collection that could not be worn today, or in years to come. Her gowns - almost all full-length: no yo-yo-ing hemlines - speak of the classical austerity of ancient Greece while revealing the voluptuousness of the body; a tantalising combination.
Madame Gres abhorred scissors. She draped her figures in a continuous length of fabric, in the immemorial manner of the classical world. Drapery, she used to say, makes a woman look slimmer and adds at least two inches to her height.
Her signature was the multitude of tiny pleats in her skirts, which gathered in severe verticals when still, like the fluting of a marble column, yet were capable of springing to life at the slightest movement. A single evening dress might have over 1,000 pleats and require over 300 hours of hand-stitching. Her bodices, when not similarly draped, a la Grecque, sported a daring decolletage or were cut out to reveal the midriff or flank.
Those exposed midriffs of hers date from the Sixties and Seventies. They are at least as sexy as anything Liz Hurley wore in the Nineties and a hundred times less tarty. She once - back in 1954 - designed a dress with one breast exposed: and very dignified it was. The see-through dress on page 31 also dates from the Fifties.
She often worked throughout the night, winding continuous 12- or 15-metre lengths of silk jersey cloth round wooden mannequins made to the measurements of her clients - the Empress of Iran, Marlene Dietrich, Princess Grace of Monaco, Nancy Mitford, the Duchess of Windsor.
Mme Gres was born Germaine Krebs in Paris and originally trained as a sculptor, her middle-class Jewish parents having denied her her dream of becoming a ballet dancer. She said: "I work with my hands, with a mass of fabric, like a sculptor with clay ... a fabric has character, its own life. By touching it I know what I am doing, but I can't make it do what it does not want to."
In 1958, oblivious of Dior's "New Look", which had set the fashion world agog the previous year, she travelled to India, adopted its bold colours and also advised Indian weavers on textile designs that would be acceptable in Paris. In the spring Paris fashion shows the following year, sari-like designs appeared on her catwalk - and also on those of Dior and Lanvin.
She herself never sought to discover what new designs other couturiers were hatching for their next collection. She did not need to. She was above fashion.
Richard Martin, curator of the Metropolitan Museum of Art's Costume Institute, mounted a retrospective exhibition of her work in New York in 1994, the year after her death, using the Met's outstanding collection of her costumes. He says: "What she was about was a kind of anti-fashion. She did not see fashion as excitement, frenzy or even caprice. Her work is untrammelled by commerce or compromise.
"Her dream was of the ancient Greek marketplace, not the modern Paris street corner. The Grecian draped dress was her emblem for most of this century. It had a dynamism, an expressiveness all its own. I see in it voluptuous excitability, pensive sexuality, repressed eroticism. It is a perfect neo-classicism. But she is not timeless; she transformed time."
Mme Colette Picco was taught dressmaking by Mme Gres, worked in her Paris studio for 23 years and hand-stitched her last dress, in 1988. She says: "Mme Gres was timid and reserved, like a mouse in a box. Instead of surrounding herself with assistants when she worked on her designs, she would shut herself away in the studio with her mannequins, rolls of cloth and hundreds of pins. Then, having worked all night, she would show us what she had done and say, 'What do you think of that, mes petites?' She was never satisfied with her work. Perfection was her aim and she was rigorously self-critical. One of her standards was that the back of a dress should look as beautiful as the front.
"There was a calm about her. She never breathed down our necks. She taught me everything, from A to Z. But making drapery is a lost skill, there are no more apprentices. I regard myself as the 'derniere drapeuse'."
Mme Gres opened her studio on the Rue de la Paix in 1941, having moved from the Faubourg St Honore where she had traded under the name Mademoiselle Alix. She had been discovered early: when she was 17 a prestigious buyer from Macy's, the big American department store, spotted the designs she had been passing round among her friends and signed her up for two years.
Her adopted name, Gres, was a partial anagram of the christian name of her Russian husband, Serge Czerefkov, whom she married in 1939. He was a mysterious artist who deserted her after the birth of their daughter, Anne, and resorted to travelling in exotic climes such as Polynesia.
Her studio was the opposite of exotic. While other couturiers had salons with garish shop-fronts, hers was tucked away up the stairs of an apartment block with, for a time, not even a nameplate. The interior was all white, a colour she loved. "White for me is peace," she said, "order and peace." Mme Picco recalls that when Mme Gres wanted to be alone with her mannequins, even her staff got no reply when they rang the bell. They had to wait patiently for her to let them in.
Mme Gres did not mix with the beau monde of the time and avoided publicity. Attending even her own fashion shows she found barely tolerable. She had a horror of photography and forbade it; newspapers had to assign sketch artists. When she did appear at her shows, she might have gone unrecognised but for her jersey turban. She always wore one - an emblem of the unchanging basics of fashion. When she wore one with a black robe, it made her look like Mother Teresa, incongruously hinting at the religious zeal she brought to her work.
Her death, after spending her last days in an old people's home in the South of France, was shrouded in the same secretiveness that characterised her life: her daughter failed to announce it until the following year.
In some of her designs one senses that Madame Gres has let her sculptor's instinct run away with her - she sometimes lumps wads of fabric on the shoulder, neckline or bust. But it is only these that fall short of timelessness. The rest epitomise age-old ideals that couturiers may, one day, rediscover.
!The collection is expected to raise pounds 100,000; estimates range from pounds 300 to pounds 8,000. The auction is on Thursday at 7pm. Viewing today (2-5pm), Mon (9am-4.30pm), Tues (9am-8pm), Wed (9am-4.30pm), Thurs (9am-4.30pm). Christie's, 8 King Street, SW1 (0171 839 9060).