I found what looks like a very large gall (irregular shape, about 15cm across, 6
high) on the floor of a mixed wood. If I could I'd put a pic up here but don't
know how.

It has a woody/leathery texture, somewhat leaf-like, except that it is like 2
containers open at the 'far' ends, either side of a hard point ith a spot where
it was apparently attached to a tree. It doesn't look, feel or smell like a
fungus, if fact it hardly smells of anything at all.

How big can fungal/viral galls become I wonder?

Ideas welcome, and I'll send photos if anyone wishes.

Cheers
Bill