Beech Barkspot (Diatrype disciformis)

Beech Barkspot (Diatrype disciformis)

Observation - Beech Barkspot (Diatrype disciformis) - UK and Ireland. Description: I think this is a rotting beech twig. I'd like to identify the fungus which is producing the black spots just under the top layer of the bark. Can anyone help, please? Edit: title changed to match Dorset Mushroom's ID - thanks.

I think this is a rotting beech twig. I'd like to identify the fungus which is producing the black spots just under the top layer of the bark. Can anyone help, please?
Edit: title changed to match Dorset Mushroom's ID - thanks.