Yellow crustose lichen found on gravestone. Photo taken in icy conditions
Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
No interactions present.
Did you spot test with K to make sure it was a Caloplaca rather than a Candelariella?
I still consider the above photo most likely to be C. flavocitrina.
However,since I posted my ID above, the concept of "C. citrina" in Britain has changed. It is uncertain whether true C. citrina occurs in Britain at all. It is probable that the bright yellow species that we have called "C. citrina" is actually C. austrocitrina. There are also other species in this group.
To add to the fun, this entire group of species has been moved to a new genus. So the ID for the photo above becomes Flavoplaca flavocitrina.
Lat/Lng: 51.0, -2.5
OS grid ref: ST7128