Lucy Wills was one of a pioneering generation of women in medicine and medical research in England. After a double first honours degree in botany and geology from Cambridge in 1911, she travelled to South Africa, where she worked as a nurse during the First World War. Wills then gained a medical degree in London in 1920. By the late 1920s she had developed an interest in haematology and began travelling to India to investigate pernicious anaemia in pregnancy. There she identified a substance often called ‘the Wills’ factor’, which was later recognised as folic acid. Wills undertook a placebo trial of routine iron supplementation in pregnant women during the Second World War, hampered, but not stopped, by bombing. In retirement, she continued to study nutritional effects on health in South Africa and Fiji.