Someone living in Llanelli, Gaynor Phillips, sent these pictures to Isabel Macho wondering what they might be. They do not have gills but spongy pores so some kind of 'bolete'. The stipes seem to have dark speckling like a Leccinum species. The main clue is the tree which seems to be a species of Poplar.
A fungus that fits would be Leccinum duriusculum Slate Bolete which is mycorrhizal with species of Poplar and the common name describes the cap colour. An uncommon bolete.