First spotted dangling from the underside of the road a couple of metres above in an underpass. When it reached the ground, it just walked steadily away - didn't run, didn't freeze. It looked very strange, but I wonder if it was just a very large, very pale redback.
It didn't really look like a redback (although you don't usually see them on the move), but it seemed to have similarities to sighting 4249130 which is also quite large and has a wrinkly abdomen.