  The advent of sensitive polarimeters on large telescopes has led to a
revolution in our understanding of active galaxies over the last 20 years. In
the case of powerful radio galaxies the deep polarimetric measurements made
possible by the new technology have: (a) provided the most direct evidence to
support the unified schemes for powerful radio galaxies; (b) enhanced our
understanding of the colours and morphologies of radio source host galaxies at
all redshifts; and (c) provided key information about the kinematics and
geometries of the scattering regions on a sub-kpc scale.
