Recent advances in modelling the effects of anisotropic energetic ion distributions have enabled the development of a complete coherent physics explanation of sawtooth stabilisation in both conventional and spherical tokamaks. As an example, a complete model has been developed to explain the asymmetric stabilisation of sawteeth with respect to Neutral Beam Injection (NBI) direction in the Joint European Torus (JET). This asymmetric sawtooth stabilisation arises because of both the destabilising contribution from the counter-passing ions and the strong modification of the non-adiabatic stabilising contribution of the trapped ions due to flow shear. The fast particle effects including pressure anisotropy, sheared flows and the adiabatic response to the internal kink mode have been modelled in general toroidal geometry for the first time.