An unidentified white crust fungus growing on a small dead oak tree (Quercus sp). It had a texture rather like cream cheese.
I took this specimen:
This yielded the following spores (magnification x600, field width 86um):
These are about 5.5 x 5um.
The basidia have 3 sterigmata (x600, width 86um):
And the hyphae have clamp connections(x600, width 86um):
First photo and specimen taken in the Wilderness, Whiteknights Park, Reading, UK, on 2014-01-11.