Porcelain Fungus (Oudemansiella mucida)
Often considered as growing specifically on dead Beech (Fagus sylvatica)
This is the second time I have found it on living Sessile Oak (Quercus petraea)
Both times on the oaks between the canal and river surrounding the playing fields nr Hollas Lane.
A very attractive fungus with a glossy white cap.
The gills can be seen through the thin cap giving a striate appearance to the bottom edge.
Here you can see the stem ring and the distant gills.