  Multi-wavelength imaging and spectroscopy of the z=0.708 radio galaxy 3C441
and a red aligned optical/infrared component are used to show that the most
striking aspect of the radio-optical ``alignment effect'' in this object is due
to the interaction of the radio jet with a companion galaxy in the same group
or cluster. The stellar population of the red aligned continuum component is
predominately old, but with a small post-starburst population superposed, and
it is surrounded by a low surface-brightness halo, possibly a face-on spiral
disc. The [OIII]500.7/[OII]372.7 emission line ratio changes dramatically from
one side of the component to the other, with the low-ionisation material
apparently having passed through the bow shock of the radio source and been
compressed. A simple model for the interaction is used to explain the velocity
shifts in the emission line gas, and to predict that the ISM of the interacting
galaxy is likely to escape once the radio source bow shock has passed though.
We also discuss another, much fainter, aligned component, and the sub-arcsecond
scale alignment of the radio source host galaxy. Finally we comment on the
implications of our explanation of 3C441 for theories of the alignment effect.
