It is fair to say that the Sixties would not have swung so much if it had not been for Marit Allen. An innovative and meticulous journalist, she was the brains behind many of the epoch-

making images of the time. Her sharp visual sense served her well when she later worked as a costume designer. Hard-working and gifted, she brought about 40 films to life through her accurate and atmospheric costumes.

Half-Norwegian, half-English, Marit Grimsmo Allen was born in Cheshire in 1941. She grew up with a passion for fashion magazines. After school and a period studying in Grenoble, she moved to London where, in 1961, she found herself a job as the fashion assistant at Queen magazine.

Even on the lowest rung of the magazine's hierarchy, she turned heads. So impressed was the Editor Beatrix Miller with Allen's work that she quickly gave her control of the About 20 pages, which Allen used as a showcase for young designers and photographers.

The distinguished Vogue Editor Grace Coddington, who credited Allen with getting her the job, believed that it was Allen who moved fashion away from its stuffy Fifties outlook — “She championed young designers and was always well admired in the industry.”

Photographers liked her maverick approach to fashion journalism too, and Allen soon made a name for herself as a playful young writer. When Miller became Editor of Vogue in 1964, she took Allen with her. Sandy Boler, who became one of Allen's new colleagues at Vogue remembered the day she arrived: “I got a big shock. She looked like an imp, a fairy, she set the room alight.”

As well as looking the part, Allen got to work on revolutionising what stylish women read. In her decade as Vogue's fashion editor she worked closely with David Bailey and his girlfriend, the model Jean Shrimpton, as well as with Cecil Beaton and Twiggy. It was Allen's idea to put Twiggy up on the country-house mantelpiece for the now famous Beaton shot.

The Young Idea pages on which she worked at Vogue reflected Allen's quest for a new youthful face for fashion journalism. Though successful, she was not lofty. She was, for example, the first Vogue fashion editor to write her own captions. Boler remembered one in particular that went with a shot of a white girl wearing a white afro wig — revolutionary in itself. The caption read “Afrodizzyaction”, and everybody loved it.

Not one to conform to received ideas, Allen was perhaps the first fashion journalist to be photographed for her own stories, something not done in the 1960s. She demonstrated a similar radicalism in her own fashion style. Her colleagues at Vogue remembered how Allen somehow managed to make spectacles a fashion accessory when everyone else would rather squint than be seen wearing glasses.

One of Allen's favourite designers was John Bates. It was he, not Mary Quant or Courrèges, who came up with the miniskirt, she said: “He bared the midriff, used transparent vinyl and raised the hemlines.”

Bates and Allen became close friends, and he designed and made Allen's wedding dress when she married the film producer and agent, Sandy Lieberson, in 1966. The couple had three children before divorcing in 1983. As a working mother, Allen's career changed direction in 1973 when the director Nicolas Roeg asked her to design the costumes for Julie Christie in the film Don't Look Now. Allen soon established herself as a prolific costumier and she continued to work right up to her death. She worked on about 40 films, and was nominated for a Bafta and two Emmy awards.

She established a strong relationship with the film director, Ang Lee, and the pair worked together on many films. Such was her commitment to the worn-in look for Brokeback Mountain (2005) that she washed all the jeans with stones and spent hours painting dirt and grime on to the cowboy shirts. Many regard her costumes for the Little Shop of Horrors (1986) as her funniest.

Allen also worked with Stanley Kubrick on Eyes Wide Shut (1999), starring Tom Cruise and Nicole Kidman. For Mrs Doubtfire (1993) Allen had a conversation with Robin Williams about how big he thought his alter ego should be. Large was the conclusion, and Allen based the eventual look on her former headmistress and history teacher — “It was exactly how they looked,” she said.

Allen mixed in glamorous social circles. Although she partied with the Beatles and enjoyed the fashion and show business lifestyle, she maintained a dignified professional committed to her work, and this was reflected in the high regard in which she held both the film and fashion industries.

Marit Allen is survived by a son and two daughters.

Marit Allen, fashion editor and film costume designer, was born on September 17, 1941. She died of a ruptured cerebral aneurysm on November 26, 2007, aged 66