  The largest global symmetry that can be made local in the Standard Model +
3$\nu_R$ while being compatible with Pati-Salam unification is $SU(3)_H\times
U(1)_{B-L}$. The gauge bosons of this theory would induce flavour effects
involving both quarks and leptons, and are a potential candidate to explain the
recent reports of lepton universality violation in rare B meson decays. In this
letter we characterise this type of models and show how they can accommodate
the data and naturally be within reach of direct searches.
