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Published online by Cambridge University Press: 14 November 2011
We construct firstly a single tactical configuration which has the structure of the dual of the affine plane of order 4, and show how to obtain a further set of 3 such dual planes which, together with
, satisfy a certain set of intersection properties. This set of 4 dual planes is used to extend the 20 points of
to the Steiner system
= S(5, 8, 24). The construction leads to the production of involutions of the type which fix the points of an octad. It is shown that 3 involutions each of this type suffice to generate M24, each of the simple Mathieu groups inside M24, the Todd group, and all the intransitive maximal subgroups of M24.