Stereum subtomentosum possibly in Fox Wood, Dene Park

 Having a quiet undisturbed walk in Fox Wood.

Thinking this might be Stereum subtomentosum, although I didn't get any obvious yellowing it did sort of gradually turn a little darker over a few hours in the house. The decision was mainly guided by the narrow attachment of the bracket to the log, about 5 mm across on a 40 mm bracket.

The upper surface is tomentose, but not very obviously so, which fits with FOTE. Oddly enough however, not even a mention of this species in Geoffrey Kibby's book.

The undersides:

The brackets had dried quite hard and woody 24 hours later.

Updated a month later - today I definitely thought I saw a yellowing when the hymenophore was rubbed hard. This however was particularly obvious when I tried a very young cap indeed, that hadn't yet even developed the red-brown colours of the mature cap. Examples are towards the top right, with one top-left. That's the trick! p. 972 FOTE.  

In Buczacki, there is mention of a black line between the hymenophore and the tomentum. I saw little sign of this on the cross sections I cut, except possibly in one section on the "older" tissue near the stipe, so I am not sure how useful this indicator might be.  

In the photo below you can see older and younger caps. In the older caps the white edge is now much less clear, and the central section near the stipe is now much more green-grey.

Be careful - on Google Images there are much paler brackets to be found - the bright red-brown of these caps may not be characteristic of the species.