Wow - thats a great find Rob!
I didnt know that Cassia contains essential oils but logically this must be the answer to all of the inconsistencies with cassia bark
Looking forward with Baited Breath to reading your report!
I bet that stuff isnt cheap.... 
Kind Regards
Mick
I think you are right Mick. Reckon it'll work both ways. So, it seems possible I have seriously underestimated the potency of my recent cassia bark purchases (and probably some earlier). An idea is that the cassia may cancel out, or mute, some/all of the other whole spices. I will be making another batch of MK I gravy next week to check this. This time with less cassia.
In the meantime I have made a Balti pork and mushroom (vindaloo) for tonight, in readiness for next week's adventures. This will definitely clear the tubes

Rob