Thanks. It is a big fresh, fleshy one. I’m not going to eat it without being certain.With the proviso that no-one should take advice on the edibility of mushrooms based on a couple of photographs, least of all from me (LOL), I would say it’s an Elm Oyster Mushroom (Hypsizygus ulmarius).
Those are edible and distinguished from other oyster mushrooms (Pleurotus genus) by the fact that the gills terminate at the junction with the stem. That’s what I see in the second picture. On other oysters, the gills run continuously into the stem without a clear termination.