It wasn't built to last more than 30 years, and it's now coming up to its 50th birthday.
It just doesn't work in London's damp, cool climate. The sharp angles preclude keeping anything too big and the lack of heated dens prevent keeping anything too small or too heat sensitive. And of course as a walk through aviary anything too sensitive to disturbance can't be kept.
It would work in the Gulf or Nevada. As I said elsewhere, a sheikh or a move mogul who'd be excited about owning something part-designed by the Queen's ex brother-in-law would be a Godsend to ZSL.
I've never seen a walk-through aviary where I was more interested in the aviary than its inhabitants until I visited London Zoo. The fact that most of the species are ground-dwelling and the path cuts through the upper reaches makes viewing a bit hard (the bald ibises sunning themselves at the top were cool to see) and the lack of any real theme makes it seem like an afterthought to actually have any birds in there at all. I liked it though and I would hate to see it destroyed. Nothing like this will ever be built again, like their elephant house and penguin pool, and should be kept for that alone in my mind.
I've never seen a walk-through aviary where I was more interested in the aviary than its inhabitants until I visited London Zoo. The fact that most of the species are ground-dwelling and the path cuts through the upper reaches makes viewing a bit hard (the bald ibises sunning themselves at the top were cool to see) and the lack of any real theme makes it seem like an afterthought to actually have any birds in there at all. I liked it though and I would hate to see it destroyed. Nothing like this will ever be built again, like their elephant house and penguin pool, and should be kept for that alone in my mind.
If this was at Whipsnade or in East Berlin, ie with hundreds of acres around, fair enough. But it will be hard enough maintaining London as a zoo of any substance without preserving structures as museum pieces. In any case, unlike the two buildings you talk about, the structure won't last.