In Oxford in the 1950s, there was a fantastic doctor, who was very unusual, named Alice Stewart. And Alice was unusual partly because, of course, she was a woman, which was pretty rare in the 1950s. And she was brilliant, she was one of the, at the time, the youngest Fellow to be elected to the Royal College of Physicians. She was unusual too because she continued to work after she got married, after she had kids, and even after she got divorced and was a single parent, she continued her medical work. And she was unusual because she was really interested in a new science, the emerging field of epidemiology, the study of patterns in disease. But like every scientist, she appreciated that to make her mark, what she needed to do was find a hard problem and solve it. The hard problem that Alice chose was the rising incidence of childhood cancers. Most disease is correlated with poverty, but in the case of childhood cancers, the children who were dying seemed mostly to come from affluent families. So, what, she wanted to know, could explain this anomaly? Now, Alice had trouble getting funding for her research. In the end, she got just 1OOO pounds from the Lady Tata Memorial prize. And that meant she knew she only had one shot at collecting her data. Now, she had no idea what to look for. This really was a needle in a haystack sort of search, so she asked everything she could think of. Had the children eaten boiled sweets? Had they consumed coloured drinks? Did they eat fish and chips?