John Riley had commented: Thanks for the image - I 've seen it before but not at such a good resolution- which newspaper is it from ? It's interesting to note that there is a chimney stack asymmetrically located at the junction of the central bay and linear factory block (A) - evidenced on both photographs - also a door way below the steps to the side bays (B) - I am unsure whether there was also a single stack serving the offices or whether feature C was architectural decoration to the central bay parapet.

What does your red dotted line on the second picture indicate?

The chimneys make sense since there would at least need to be flue for the water wheel basement (viewing platform) fire and I can't imagine the central offices would be without some heat.   I had noticed what seems to be a doorway under the steps up to the right promontory.  We are currently working on the cellar area below that which is the mill end of the tunnel bringing the auxiliary power from the Waterloo wheel.   At the moment there is no evidence of a ground level floor in that promontory and it maybe that the door under the stairs led onto a flight down into the cellar/ shaft service areas.

Time for you to pop down and have another look!