Although I went there a couple of times in the 1960's, I don't remember this Folly- the 'Hollywood Tower' of the estate's name presumably. I do remember the Okapi enclosures, and some very basic White Tiger housing. I cannot remember the 'Giraffe' house though. I do wonder if they actually had Giraffe there though its possible, given that there were Black Rhino(single) Okapi and Tigers as well as the Cranes and other assorted odds and sods.
It certainly looks to be a good site for further development- they have just been sitting on this place ever since they originally purchased it.