SlipperFan and Mr. Wellenstein,
I'm certainly no expert on taxonomy, but this looks more like hookerae to me. I'll give you the reasons why, and perhaps we can get this sorted out.
First of all, there are a couple points of interest in Rolfe's description of volonteanum, compared to hookerae (quoted in Cribb 1987) "... the petals are broader and more obtuse, the lip a little constricted below the horizontal mouth and the staminode quite orbicular, without notches."
It was the staminode that interested me first.... and I've done a little comparison (but there seems to be plenty of variation here).
Hookerae seems more frequently to have a notch at the top of the staminode, like this:
And I think that SlipperFan's is similar:
The volonteanums that I've found don't have the same notch, usually:
That doesn't seem like the soundest foundation for species distinction, to be sure. They all seem to have some constriction "under the mouth". The red/purple under the leaves seems to be the simplest distinguishing feature. It is more common in volonteanum (but there is reported to be some overlap).
Anyway, that's my take on the issue... I'd be interested to hear others' opinions.
As Ever,
Matthew Gore