If you're observant as you walk up to Blackheath from Charlton as you enter the Standard you'll notice a gap in the run of houses on your left along Charlton Road. Looking off to your right you'll see that there's a road, Invicate Road, running almost directly opposite it. It looks almost as if the road used to cross Charlton Road and run between the houses.
If you check it out on Google Earth you'll see it really clearly indeed. There's a very obvious gap running in a straight line all the way south to Shooters Hill Road.
It puzzled me when I noticed this at first and I wondered if it might be some old road or railway that had been removed.
However a Google Earth session shows that the north end of the gap lines up with where the rail tunnel emerges back above ground. It's also easy to image a curve linking up the southern end with the entrance into the tunnel to the east of Blackheath station.
As far as I know that railway has always been in a tunnel. However could the gap above it be because it was dug using the cut and cover technique? That is rather than tunnelling you dig a big trench and then build a roof before covering it back over.
Looking around on the internet I can find mention of some kind of accident in the tunnel in 1850 but with no details. The station dates back to 1849 so that does suggest that the railway never ran above ground.
Does anyone know?