Dr. Dewar has made original contributions to the basic theory of nonlinear processes in plasmas using novel mathematical methods. In particular he developed a Lagrangian method for calculating the interaction between a wave and an inhomogeneous background fluid which has also found application in other areas of fluid dynamics, and he pioneered the use of Hamiltonian perturbation theory for simplifying the description of particle motions in the presence of large amplitude plasma waves. He has also contributed significantly to the development of analytical and computational techniques for assessing the stability of toroidal, magnetically confined fusion plasmas.