Some people like to spot trains or busses, some like to take photos of fancy iron work. Christopher Howse on the other hand looks for opercula, coalhole lids. These are circular cast iron plates which lock into a metal ring in the ground. These typically only can be opened from the inside so that people can’t steal the coal.
I spotted these quatrefoil examples on a Victorian street in Richmond, Surrey.
One nice feature of these plates is that the often have the makers details around the circumference, this allows a more detailed peek into history. Most people don’t have a use for a coal hole any more so are removing their unused opercula. Christopher is documenting the opercula before people rip them all up and sell them off for scrap.
If you see any of these on your travels drop a picture on twitter with the tag #opercula and the street name, you can see more examples on Christopher Howse’s feed.