@amur leopard Yes, its bigger perhaps than it looks. Each of the 'drums' was an Elephant stall, and a dry moat ran along the front of all four. There were skylights in the roof. I think somewhere in the gallery there is a photo or two showing the interior in use.
@DavidBrown I can't remember exactly but Wikipedia say the newer Elephant house was 'opened'(it held the white rhino herd previously) in 1996 so presumably around then. Of course this old Lubetkin house did have an outside paddock by then, though for many decades previously it hadn't. The elephants were exercised outside and/or gave rides instead.