Not to 'compete' with the other current Arnotts thread, but as it reminded me, it's only logical I post here to in some way bring closure to this long-running saga
I can now confirm for definite, as was suggested earlier by some, that this
is what what built at the turn of the last century:
A central tower flanked by two smaller terminating pavillions.
The IAA has a picture of Henry St prior to 1916 clearly showing the building above in all its glory, with the now-demolished right-hand tower standing in the distance.
The vast building as depicted on the bag, as everyone knew, never existed.
It also explains why there are still interior decorative cast iron columns continuing into the 1960s part - as far a I can make out they run precisely to the depth that the terminating tower and extra bays would have extended to. Clearly they were demolished to make way for what is a mere curtain wall
Didn't have time to check out the original 'bag plans' for the building - work for another day.
Only then will the Arnotts Mystery be truly solved.......