These enigmatic concrete semi-ruins at Clydevale turned out to be what is left, there, of a late 1930s government initiative to help the war effort by growing linen flax (pretty much the same plant grown for Linseed oil) so the fibre could be sent to Britain for all the uses it had during war-time. The most romantic use was for the linen fabric covering of the wings and airframe of such aircraft as the Spitfire, the Hawker Hurricane and the Wellington Bomber. This big tower block was apparently part of the boiler room. It appears to me that the retting took place in water tight concrete cells of which there are four, loaded and unloaded through gasketed sliding steel doors with toggle clamps.
There is quite a bit about this wartime industry on the Net. One story I was told was that a (possibly just the once?) shipment of frozen meat due to ship out of Dunedin was off-loaded and replaced with linen fibre at the last minute - such was its value to the industries in England that used it during the war. Possibly an incoming ship was lost at sea and the flax went instead of the meat! Rumbling tummies down at 't mill.
These photos are just to place the activity on the map - an effort to spatially define known and not so well known historic engineering works undertaken in NZ really. Much of my Panoramio activity is no more than that. I certainly do not pretend to be an expert.