Patches of white crustose thallus on trunk of tree at edge of wood. Black lirellae, some branched, on each patch. Possibly Graphis scripta.
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.
Thank you for pointing towards Opegrapha species. Shall try to follow up.
I'd be surprised if was this species, which I have semi-convinced myself I can recognise in the field (but I don't always check to see if I'm right!) It (usually/always?) has crowded lirellae that remain slit-like rather than developing the more open appearance seen in your photos.
If the mature spores are 3-septate (immature spores may not have become fully divided), then there are other possibilities with more open apothecia (eg O. herbarum).
Spore measurements (length and width ranges) might offer more clues.
The likely I.D. at present is your 'Opegrapha' and that seems as detailed as possible at present (especially knowing my limitations with a microscope!).
Thanks for the pointers for Opegrapha atra and many thanks again for all the help and information passed on through your consideration of observations posted. Very much appreciated.
Lat/Lng: 52.4158, -0.0698
OS grid ref: TL313815