Ambrose came to Canada in 1951 when Franca, with whom she was collaborating on the book Beginners, Please! (published 1953), accepted a position as artistic director of the National Ballet. During the 1951-52 season Ambrose performed a number of design, promotional and public relations tasks for the company in an unofficial capacity. She also nurtured the inexperienced dancers, helping to heal their injuries, cooking meals for them and training them in the art of stage makeup. She joined the company officially in September 1952 as public relations officer, and a year later, as artistic adviser, designing ballets such as Swan Lake, Coppelia, Giselle and The Nutcracker. Ambrose designed and dressed over 30 ballets during times when budget constraints made it necessary to exercise her considerable ingenuity in finding the materials to "make a silk purse of a sow's ear."
After the 1961-62 season Ambrose took a sabbatical from which she never returned. Upon hearing of her untimely death, Celia Franca cabled to her surviving relatives: "Ballet world has lost one of its most talented and best loved artists."
Author IAN ROBERTSON