Maurice Stevenson Bartlett. 18 June 1910 — 8 January 2002

The last 70 years or so have seen the vigorous development of mathematical models in technology, epidemiology, economics and the natural sciences whose dynamics are intrinsically random in some sense; life is such. The study of the behaviour such models might demonstrate is that of stochastic processes. The converse task, to determine an appropriate model from reallife behaviour, is that of statistical inference.Maurice Bartlett was a pioneer in these disciplines whose insight and power as a problemsolver brought him an international reputation. He made basic advances in the study of stochastic models and the statistical analysis of data that they might represent, in particular for models with a dynamic element, so allowing the study of phenomena that evolve in time. Specifically, he made early key advances in what is now called multivariate analysis, developed time series analysis, produced a coherent theory of stochastic processes (making innovations whose significance was recognized only years later) and studied stochastic models of, for example, the growth of population, the course of epidemics, and systems with a spatial dimension (such as vegetation or meteorological variables). A much less tangible phenomenon which never lost its fascination for him concerned methods for the identification of ‘factors’ in psychology or performance. These are just the major headings in a series of investigations in which he simultaneously developed stochastic theory, evolved statistical methodology and pursued the particular application to a conclusion.As well as enjoying a unique reputation among his colleagues, Bartlett, although an undemonstrative man, evoked a lasting warmth and firm loyalty in all who worked with him.