  We consider a supersymmetric type III seesaw, where the additional heavy
states are embedded into complete SU(5) representations to preserve gauge
coupling unification. Complying with phenomenological and experimental
constraints strongly tightens the viable parameter space of the model. In
particular, one expects very characteristic signals of lepton flavour violation
both at low-energies and at the LHC, which offer the possibility of falsifying
the model.
