 Fox was an active member of the Institute of Mathematics and its Applications from its beginnings, as a member of the Council and as an editor first of the main "'IMA Journal" and later the specialised Journal of Numerical Analysis, started in 1981.The IMA marked his retirement from Oxford in 1983 by a special IMA symposium on 'The contributions of Leslie Fox to numerical analysis'.His interests extended to mathematics in schools and he participated the development of the School Mathematics Project, and was active in the local branch of the Mathematical Association, of which he was President in 1964.