Some people have also said this house has a preservation order on it too-but it was only constructed in the 1960's so I'm not sure that it has.
Filling in the moat would give them a lot more space. Large glass viewing windows could be installed- but that's all major expense, whereas what they have done is largely cosmetic- though its a big improvement.
From what I've seen of orangutans, they're a dab hand at demolition. Surreptitiously provide them with a few sharp rocks and they could do what people may not be allowed to do Alternatively, maybe it will contract concrete cancer. The alterations are an improvement however.
I think you wil find that bongorob is correct.As we were told that my the director and the collection manager,when the 2 of the showed the Bartlett Society round!