I don’t really know what this is, but I snapped it. It’s a stone in the central reservation of the barrier at the west end of the railway bridge at the junction where New England and Old Shoreham Roads meet. I guess, technically, that it’s on New England Road.
It obviously has a railway connection. LB&SCR (London, Brighton and South Coast Railway) is our clue there. But otherwise, I’m not sure at all what it means.