You lot make me feel ancient. I won't repeat everything I said in the other thread, but I can fill in a couple of points.
I first visited in the late fifties (when I was 7 or 8) - nearly 50 years ago now

I remember poring over the zoo map when I got home (no guide book in those days, just a map). I was most upset that we'd missed something: I remember complaining to my family 'we saw the buffalos, but we didn't see the buffet'

(I don't know why they called the restaurant that, perhaps it was a 50s thing).
There were originally two bear enclosures, where the children's playground, Mauritius kestrels and snowy owls are now. They were squarish concrete islands with a deep dry moat and a concrete back wall - quite small and very ugly. They held brown and Himalayan bears. The polar bears had quite a good enclosure, by the standards of the day, where the right hand half of the 'Europe on the Edge' aviary is now. The back wall of the polar bear enclosure and the raised walkway on the sea-lion's side are still in use.
The sun bears lived in the round enclosure where the yellow mongooses are now - right in front of the main entrance (which is now the staff entrance, of course). Bongorob posted a photo in the Gallery. The bear enclosure by Flag Lane, on the condor site, was built later for Kamchatka bears. It was basically a concrete wall around a concrete base with a pool. It was larger than the other bear enclosures, but no lovelier. If I remember rightly, you could walk all round the top of the wall.
At that time the Tropical Realm had not been built. There was just the chimp islands and their house was behind (there's an old photo of that in the Gallery too). The orangs, and eventually the gorillas, had the island nearest the camels, where the current chimp night quarters are.
I think the only animals which are still kept in the same places now are the lions, tigers, chimps and sea-lions - plus the owls and the aquarium; although of course the enclosures have all been modernised.
Alan