In advanced tokamak operation the ultimate performance limit is set by Resistive Wall Modes (RWMs). A damping term arising from relative rotation between the plasma and mode determines the stability of the RWM and cross machine experiments, between DIII-D and JET, aimed at determining this damping are reported. Comparisons of the amplification factors of applied resonant fields show good agreement between JET, DIII-D and calculations with the MARS-F code using a kinetic damping model. A second comparison using n=1 magnetic braking to determine the critical velocity at which RWMs are destabilised is also presented. The interpretation of this result is discussed in view of the fact that the applied fields may be playing a role in driving the observed mode. The results can however be interpreted as providing a threshold for applied error fields to destabilise RWMs and illustrate the importance of error field correction at high-b in ITER.