Looking at the map and bearing in mind East Dulwich and Herne Hill are in zone 2 it looks like the zone has been narrowed for our part of London. Whats the logic of why we are in zone 3 and East Dulwich and Herne Hill are in Zone 2. We must be nearer the city of London?
East Dulwich station is just inside Zone 2. The border (when buses were included in Travelcard Zones) is the Goose Green roundabout.
Zone 4 starts at Cobbs Corner, which is why Sydenham is just inside Zone 3, although Crystal Palace is shared between 3/4 after it was decided to move it into 3 to keep costs down for passengers.