The pyridinophane complex [Mn(Py2N2)(H2O)2]2+ catalyses the disproportionation of H2O2 in aqueous solution over a wide pH range. Kinetic investigations reveal an induction period, which is proposed to involve the formation of a hydroperoxo intermediate, as well as evidence for catalyst self-inhibition. A catalytic cycle involving mononuclear intermediates has been proposed. Spectroscopic investigations under turnover conditions are consistent with this proposal and show that the resting state of the catalyst is a mononuclear MnII complex. The robustness of the catalyst is evidenced by its ability to achieve turnover numbers of 58000 in aqueous solution.