White Crustose on brick wall facing North
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.
Probably Diploicia canescens but can't enlarge the photo enough to check details.
Its growth form is known as placodioid - crustose but with lobed margins
I initially thought it might also be Aspicilia calcarea, but then I saw that this one doesn't have the lobed margins. So once again thanks for the lesson.
Lat/Lng: 51.403904332142, -1.2620866298676
OS grid ref: SU514674