  We observe that the flavour symmetries of the Standard Model gauge sector,
broken as they are in the Standard Model Yukawa Lagrangian, naturally suppress
baryon and lepton number violation at low energies and, simultaneously, make it
accessible at the LHC through resonant processes involving at least six
fermions from all three generations. We establish a model independent
classification of such transitions and identify two classes that give rise to
particularly clean LHC signatures, namely $\bar t \mu^+ e^+$ and $\bar t \bar
t$ + jets.
