Textiles were not what fashion was about in the first half of the 1960s, when an adequately outrageous outfit could be extracted from a short, narrow length of Acrilan, Dicel or Bri-Nylon. That was not the style of Gina Fratini, who has died aged 85; her interest was in the stuffs themselves, preferably natural fibres, in quantity. She became a professional designer in 1964 and was ready with bolts of cotton and silk as skimpiness in synthetics peaked and lost novelty around 1967. Fratini then became an important player in a London-based, fabric-intensive, fantasy style over the next few years when it was unremarkable to go about daily business dressed as an illustration by Kate Greenaway, in an ample lawn smock with apron over matching pantalettes. Or a voile and lace teagown. Even after daywear returned to relative reality in the 1970s, Fratini kept an evening-wear clientele who felt safer after dark in her body-flattering drapery.

Princess Diana in Gina Fratini, on a tour of Canada with Prince Charles in 1983. Photograph: Tim Graham/Getty Images

Despite the Italian name – Gina was short for Georgina, while Fratini came from her glam second marriage – she was imperial-era British, the daughter of a well-connected colonial service officer, Somerset Butler (son of the 7th Earl of Carrick), and his wife, Barbara (nee Hood). Gina was born in Kobe, Japan, and brought up in Burma and India (she never forgot the soft, natural fabrics of those countries) until sent home to boarding school, Owlstone Croft in Fairford, Gloucestershire.

In 1947, she was among the first students in the newly opened fashion department at the Royal College of Art, in London. In her final year there she met the great African-American dancer Katherine Dunham, touring the world with her troupe. Dunham took Gina on to help with costumes, designing and making exotica on a low budget.

Gina was for two years company needle-of-all-work, coming back to London in 1953, and marrying David Goldberg the next year. She dropped out of formal employment but continued making to order pretty dresses for friends. The Goldbergs divorced in 1961, and she married Renato Fratini, a commercial artist from Italy; they went out nightly, dining, dancing, encountering potential customers. The business she began in 1964 was underfunded and so improvised that she cut out and sewed at home, at first buying retail any fabrics she thought interesting or amusing, especially prints on thin cottons and silks, adding ribbons and lace. Fratini used even more yardage by cutting on the bias, a technique then out of mode. She was seldom knocked off by the rag trade as her pricey originals were difficult to copy without big supplies of the original materials.

A model wears a Gina Fratini dress, 1970: ‘I like movement,’ the designer said. Photograph: Chris Barham/ANL/Rex/Shutterstock

Fratini specialised in long, cobble-brushing dresses (according to Vogue’s Grace Coddington), theatrically inspired by masquerade and folk costumes; a touch of panto, too. Her imagination was more English – Fratini gardened, attended Ascot – than Thea Porter, less aggressive than Zandra Rhodes, more modest than wild Ossie Clark. She thought of herself as a dressmaker, and her work photographed beautifully in motion on dancing models. “I like movement,” Fratini explained. “There’s nothing more fascinating than a woman flowing instead of walking.” The merry-peasantwear suited only the young, but her concealing layers and sympathetic cut brought older clients, including Princess Anne and Elizabeth Taylor, who married Richard Burton (for the second time) in a sheer, shade-dyed kaftan. Fratini designed many custom wedding dresses in acres of pale thin cloth, although she was not asked to supply the gown for her favourite later customer, Princess Diana – Fratini claimed that the famous Emanuel wedding dress had stooped to synthetics beneath its meringue skirt, causing static. Not much dancing in that.

The Gina Fratini wedding dress worn by Elizabeth Taylor in her second marriage to Richard Burton on display at Christie’s auction house, New York, in 2011. Photograph: Mike Segar/Reuters

Her label, and personal attention, attracted princesses: besides Anne, there were Alexandra, Princess Michael of Kent, and Margaret, who wanted, but did not get, a fitted, even boned, bodice to prop the bosom. Diana commissioned evening dresses, softer than her usual graphic style, including a white chiffon “sari” – Fratini dreaming of India – for an official portrait photograph by Terence Donovan. Diana remained a personal client even after Fratini closed the company in 1989 because it was profitless. She never coped with changing fashion economics; like many London designers, she kept the small, short production runs of 1960s boutiques, the creative involvement from fabric selection to finishing, always prepared to sew the last stitches herself for a better flow. She guest-designed a little for Norman Hartnell, then retired.

She had divorced Renato Fratini in 1968, as her business first took off, and in 1969 married the Scottish comedian and theatre director Jimmy Logan (James Short), an unlikely match except that she liked to laugh a lot. It lasted until 1977. The love of her life was the singer and actor Anthony Newley; they had had an affair in the 1950s, when both were already married, stayed friends through his later marriage to Joan Collins, then reunited and lived together from 1993 until he died of cancer in 1999. “We came back together at the perfect time, but it ended too soon,” she said.

Fratini had wanted children, but they never came; hence, she said, the frock shop.

• Gina Fratini (Georgina Caroline Eve Butler), dress designer, born 22 September 1931; died 25 May 2017