Spots of Chondrostereum purpureum growing on a birch log (Betula sp).
I took the following specimen home with me:
And this yielded these spores (magnification x600, field width 86um):
These are about 6.5 x 2.5um which agrees with the 5-8 x 2.5-3um given for Chondrostereum purpureum at Roger's Mushrooms.
First photo and specimen taken in Whiteknights Park, Reading, UK, on 2013-12-14.