  We propose a variant of the Pati-Salam model, with gauge group $SU(4)_C\times
SU(2)_L\times U(1)_{Y'}$, in which the chiral left-handed quarks and leptons
are unified into a $\underline{4}$ of $SU(4)_C$, while the right-handed quarks
and leptons have quite a distinct treatment. The $SU(4)_C$ leptoquark gauge
bosons can explain the measured deviation of lepton flavour universality in the
rare decays: $\bar B \to \bar K^{(*)}\bar\ell\ell, \ell=\mu,e$ (taken as a hint
of new physics). The model satisfies the relevant experimental constraints and
makes predictions for the important $B$ and $\tau$ decays. These predictions
will be tested at the LHCb and Belle II experiments when increased statistics
become available.
