A life in ballet, particularly at its highest levels, is a ceaseless quest for perfection. The search starts at a very early age, when a youngster will learn how to skip and jump in time to music and be shown how to point a foot just so. As the years progress the student must master the minute, ever-changing relationships between head, shoulders, arms, hands, fingers, the torso, hips and lower limbs at any given moment in the dance. How the head must spin and the eyes focus to enable a serene turn. Above all, as the years go by, a dancer must use all these technical skills in the service of something more: a level and quality of artistry unique to the individual that give meaning and insight to a work of art.

Perfection, as any dancer will tell you, is elusive. Nevertheless, it and its close ally, control, are sought and prized.

It takes a special kind of physical and mental toughness to prosper in this world and Mary McKendry had it. She started learning ballet when she was eight, which was rather late given that her first...