  We postulate that the neutrino mass matrix in the lepton flavour basis is an
S3 group matrix in the natural representation of S3. This immediately requires
one neutrino to be trimaximally mixed, as suggested by the solar neutrino data.
We go on to postulate that the charged-lepton mass matrix in the neutrino
mass-basis is an S3 class matrix in the natural representation of the S3
class-algebra, leading to exact tri-bimaximal mixing, which is compatible with
data overall. The tri-bimaximal mixing matrix is seen to be closely related to
the S3 character table, and is properly the S2 C S3 table of induction
coefficients, where the S2 corresponds to symmetry under mu-tau interchange in
the lepton flavour basis.
