The luminosity of the electron-proton collider, HERA, will be increased by a
factor of five during the long shutdown in the year 2000. At the same time
longitudinal lepton beam polarisation will be provided for the collider
experiments H1 and ZEUS. These far reaching upgrades to the machine will be
matched by upgrades to the detectors. The result will be a unique facility for
the study of the structure of the proton and the nature of the strong and
electroweak interactions. The physics potential of the upgraded accelerator is
discussed here together with a brief description of the HERA machine and
collider detector upgrades.