  I shall use a few personal reminiscences of my time as a student and
colleague of Dirac in Cambridge to introduce some reflections on the nature of
research in theoretical physics. I shall discuss and illustrate the approach of
Dirac to his own research and the pervasiveness of the influence his example
has provided.
  I shall discuss how ideas produced at all stages of his career have proved to
be extraordinarily visionary, still motivating and exerting an influence on
research many years after his death. Examples include his celebrated equation
and prediction of the existence of antiparticles, the magnetic monopole and its
quantisation condition, the quantum theory of dynamical systems with
constraints and the membrane theory of the electron.
