I'm reminded of an old signal post to the south side of the Up Caterham line just down from the junction at the south end of Purley station where the Caterham and Tattenham Corner lines join. You can just about see this in the below shot from Google Streetmap - the post is right next to the Higher Drive overbridge.
It looks (see below) that the signal used to possibly be for the Up line rather than being for a down direction move along the up line, but is now replaced by a four aspect with position 1 feather on the other side of the bridge - it was never in use when I lived down there, and the video capture below is from 1989, so it's stood there some time. Anyone know when that post was last used? (possibly 1984 remodelling of the Brighton Main?)
Here's the view from a cab video from a 455, taken 1989 (Mac's Tracks on Youtube:
):
