  We have monitored the Didymos-Dimorphos binary system in imaging polarimetric
mode before and after the impact from the Double Asteroid Redirection Test
(DART) mission. A previous spectropolarimetric study showed that the impact
caused a dramatic drop in polarisation. Our longer-term monitoring shows that
the polarisation of the post-impact system remains lower than the pre-impact
system even months after the impact, suggesting that some fresh ejecta material
remains in the system at the time of our observations, either in orbit or
settled on the surface. The slope of the post-impact polarimetric curve is
shallower than that of the pre-impact system, implying an increase in albedo of
the system. This suggests that the ejected material is composed of smaller and
possibly brighter particles than those present on the pre-impact surface of the
asteroid. Our polarimetric maps show that the dust cloud ejected immediately
after the impact polarises light in a spatially uniform manner (and at a lower
level than pre-impact). Later maps exhibit a gradient in polarisation between
the photocentre (which probes the asteroid surface) and the surrounding cloud
and tail. The polarisation occasionally shows some small-scale variations, the
source of which is not yet clear. The polarimetric phase curve of
Didymos-Dimorphos resembles that of the S-type asteroid class.
