A local Tb Theorem provides a flexible framework for proving the boundedness of a Calderón-Zygmund operator T . One needs only boundedness of the operator T on systems of locally pseudo-accretive functions {b Q }, indexed by cubes. We give a new proof of this Theorem in the setting of perfect (dyadic) models of Calderón-Zygmund operators, imposing integrability conditions on the b Q functions that are the weakest possible. The proof is a simple direct argument, based upon an inequality for transforms of so-called twisted martingale differences, which has been noted by Auscher-Routin.