Identification: What shelf fungus on English Oak tree?

I'm wondering if these two fungus growths on opposite sides of the base of an old Quercus robur are Ganoderma applanatum. The scratch lines are mine, and they seem to be light greenish-brown.

I thought I had learned that polypore fungi were opportunists, but I see the Wikipedia says about Ganoderma applanatum - Wikipedia:

It is a wood-decay fungus, causing a rot of heartwood in a variety of trees. It can also grow as a pathogen of live sapwood, particularly on older trees. It is a common cause of decay and death of beech and poplar, and less often of several other tree genera, including ... oak ... .
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So these are killing the tree? Does it help the tree to remove them, or would there just be too many spores left behind to matter?

 

Hi Wendy,
It does not help the tree to remove the fruiting body. In general, by the time one sees fruiting body the part of the tree the particular species inhabits is suffused with the body of the fungus.
Some polypores are more specific about tree species and/or parts of tree inhabited than others.
The fact that it has a very white pore surface, the size and thickness, and that it is fruiting from hardwood, considerably narrows the options: I think you are right, it looks like Ganoderma applanatum. I'm hesitating partly as it is on a non-native tree, which raises the possibility of a non-native or out-of-usual-range fungus.
-frog