Professor Seneta has made substantial contributions to the probability theory of Markov chains and in particular to the theory of discrete branching processes. His work here is widely recognised. He has also worked successfully on the application of the theory of stochastic processes to population genetics. His influence has been considerable through the development of certain mathematical tools for the study of Markov chains, namely the theory of infinite non-negative matrices and of regularly varying functions. His work on the history of probability and statistics has given him international recognition as a leading authority.