Alan Cottrell (1919-2012) was a highly influential materials scientist and prominent government scientific advisor. After studying and teaching at the University of Birmingham he moved to the Atomic Energy Research Establishment, Harwell, overseeing the materials research essential to Britain’s Magnox nuclear reactor programme. In 1958 he left to take up a chair at the University of Cambridge, where he advocateda greater understanding of materials according to their underlying physics rather than the previous empirical based methods. This was a key issue in transforming metallurgy to materials science. He moved to Whitehall in 1964, rising through a series of senior posts that culminated in that of government chief scientific advisor in 1971. Here he oversaw significant changes in the funding regime that did not always meet with the approval of scientists. Later he returned to Cambridge as master of Jesus College, where he presided over the admission of women, and later as vice-chancellor of the university. In retirement he returned to scientific work and acted as an advisor to government and industry.