Crustose lichen. Margin of apothecium similar in colour to body of lichen. Apothecium reddish brown. On tree trunk. Perhaps L campestris?
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.
It may also be worth checking pictures of Lecanora chlarotera (more frequently found on trees than Lecanora campestris) on the 'Search iSpot' panel for comparison. (There are also lots of other lichens with brown lecanorine apothecia!)
Lat/Lng: 55.4733, -3.2022
OS grid ref: NT241205