Test of lepton flavour universality at LHCb

This contribution presents the $R_D{\ast}$ and $R_K$ measurements, which are a clean probe of lepton flavour universality, and the angular analyses of the $B^0 \to K^\ast {0} \mu^+ \mu^-$ and $B^0 \to K^\ast{0} ~e^+ e^-$ decays, which allow to search for New Physics in rare decays proceeding through ${\text a} ~b \to s \ell^+ \ell^-$ transition. All measurements have been performed by the LHCb collaboration using the full statistics of LHC Run I. An overview of the ongoing and future measurements is given in the conclusions.