In 1997 Walker and Boyer shared the Nobel prize for Chemistry. Their great contribution was the elucidation of a mechanism for the F1 portion of ATP synthase 1. It is significant that despite advances in the areas of mitochondrial genetics and proteomics, there are still gaps in our understanding of the overall mechanism of ATP synthesis. Among such deficiencies in knowledge is the crucial but still obscure role of the Fo component of the system. We believe that an understanding of the mechanism whereby the Fo rotor is driven by the membrane proton gradient is still an outstanding priority in bioenergetics research. Any model which purports to explain the role of the Fo sector of ATP synthase must be sufficiently detailed to permit the precise thermodynamic or kinetic consequences of the model to be calculated. Yet the model should ideally be simple enough to contain a minimum, preferably zero, number of unproveable assumptions. We present a model herein, which we believe fulfils the required criteria.