Patricia Mary McDonagh, who has died aged 80, was a well-known British fashion designer of Irish ancestry who moved to Canada in 1966, bringing with her the defiant London styles of the Swinging Sixties – the miniskirts, the bellbottoms and maxi coats – landing in terms of fashion, as she once put it, "in the dark ages" .
In the UK she established her name with two stylish boutiques, creating costumes for the Beatles and Diana Rigg in the original series of The Avengers. For nearly four decades until her death, she was a fashion figurehead in Canada known for her tailoring, her fabrics and glamorous evening wear.
McDonagh was born on St Patrick's Day in 1934 in Manchester, the eldest of four children in a family whose forebears had emigrated from Ireland in the post-famine period.
She inherited a sense of perfectionism and attention to detail from her mother, who taught her to sew and who “never praised us – we were never good enough”, she once recalled. Educated at the Loreto Convent, she studied psychology and literature for a time at the University of Manchester. In the late 50s she worked as a model in London and for the Paris fashion houses of Maggy Rouff and Jacques Heim.
Following her marriage to television director David Main and the birth of their first two children, the family emigrated to Canada where she opened a shop in downtown Toronto. She famously introduced Twiggy, a then unknown model whom she had used in the UK, to the fashion editor of the Toronto Star who was nonplussed by the coltish youngster's waiflike appearance.
Some of her more famous pieces were a T-shirt dress, a Mongolian jacket, a pea coat and a Napoleon-inspired military greatcoat worn by the governor general, Michaelle Jean, during Barack Obama's visit to Canada in 2009. Often compared to Mary Quant, she never changed her personal style and like Quant her black Vidal Sassoon bob was her signature. Occasionally seen with a parrot on her shoulder or biking around Toronto, she befriended the homeless and supported HIV and Aids charities.
She is survived by her three children, three grandchildren, her brother, Michael, and sister, Bernadette.