In the standard model of particle physics(SM), all charged leptons (electrons, muons and taus) should interact in the same way (besides effects only due to their different masses). However, this is not necessarily true in many theoretical models beyond SM. Precise tests of this lepton "universality" are being pursued at the LHCb experiment at the LHC collider at CERN, using B mesons decaying to tau leptons. A persistent deviation at the 3 sigma level from SM prediction is observed since 10 years in this area. These delicate measurements were thought to be impossible in LHCb and yet the results based on the tau decay to three charged pions which will be presented have reached the best world-wide precision in absolute terms for a single channel so far. Many exciting prospects based on this method developped at IJClab will also be discussed.