Fungal or insect damage for ID, please

Fungal or insect damage for ID, please

Observation - Fungal or insect damage for ID, please - UK and Ireland. Description: Small brown spots on the leaf of a Beech (Fagus sylvatica). They didn't seem to develop much beyond this and the tree wasn't significantly affected. Not sure if the damage is insect or fungal hence put in ? for the moment. Can anyone offer an ID of the

Small brown spots on the leaf of a Beech (Fagus sylvatica). They didn't seem to develop much beyond this and the tree wasn't significantly affected. Not sure if the damage is insect or fungal hence put in "?" for the moment. Can anyone offer an ID of the causer, please?