We construct models of leptons based on S 4 family symmetry combined with a generalised CP symmetry H CP . We show how the flavon potential can spontaneously break the symmetry S 4 ⋊ H CP down to Z 2 × H ν CP in the neutrino sector, where the choice of preserved CP symmetry H ν CP is controlled by free (real) parameters in the flavon potential. We propose two realistic models of this kind, one at the effective level and one at the renormalisable level. Both models predict trimaximal lepton mixing with CP being either fully preserved or maximally broken, with the intermediate possibility forbidden by the structure of the models. *

We extend the even weight modular forms of modular invariant approach to general integral weight modular forms. We find that the modular forms of integral weights and level N can be arranged into irreducible representations of the homogeneous finite modular group Γ N which is the double covering of Γ N . The lowest weight 1 modular forms of level 3 are constructed in terms of Dedekind eta-function, and they transform as a doublet of Γ 3 ∼ = T . The modular forms of weights 2, 3, 4, 5 and 6 are presented.We build a model of lepton masses and mixing based on T modular symmetry. *

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