Nicholas Day is a statistician and cancer epidemiologist, renowned for his influential work in quantitative epidemiology, especially of cancer. Nicholas’s main research focused on finding the causes of cancer in order to improve its treatment. In later years, he also extended his investigations to other areas of disease.

In collaboration with American statistician and medical researcher Norman Breslow, Nicholas wrote a two-volume monograph that provided a definitive account of the use of statistics in cancer research. He made significant contributions to cancer screening, where his findings form the basis of national screening policies for cervical cancer, amongst others. He was also responsible for projecting the future incidence of AIDS.

Nicholas has held many prestigious positions, including Director of the MRC Biostatistics Unit from 1986–1989. From 1997 until his retirement in 2004, Nicholas was the Co-director of the Strangeways Research Laboratory in Cambridge. He received a CBE in 2001 for his services to statistics and epidemiology in cancer biology.