  We present a model which employs the seesaw mechanism with five right-handed
neutrinos, leading to trimaximal and CP-conserving lepton mixing. Tri-bimaximal
mixing is a natural limiting case of our model which occurs when one particular
vacuum expectation value is real and preserves the mu-tau interchange symmetry
of the Lagrangian. Our model allows for leptogenesis even in the case of exact
tri-bimaximal mixing.
