I had one flower.... last year or the year before. The spathe stayed tightly closed for what seemed like an eternity until one morning when, on my way out to work, I stood on the doorstep and could smell it from 20ft!
Fingers crossed yours won't take too long (but it will probably still open overnight).
Excellent flower Andy, thanks for posting another pic now its opened Is the smell quite bad or is it bareable?? I guess being outside rather than in a enclosed greenhouse must help quite a bit with the smell.