The work on the former tapir enclosure looks to be necessary adjustments rather than any attempt to create a long-lived exhibit, which I think would be a huge mistake. IMHO there isn't really enough room on this little corner of land for a compatible, non-breeding pair of pygmy hippo, let alone if ZSL decided to keep the species in a breeding setup (separated for much of the year) using this enclosure. As someone else pointed out, the steps into water work ok for tapir, but not for hippo. I believe when Marwell built the semi-aquatic mammal house in the 80s they discovered that the hippos couldn't get into the ponds using the steps, so they had to install ramps.
So hopefully just a stopover, we'll see. If the zoo wants to avoid bad publicity a few years from now, they'd better look again at the giraffe facility next door. Really, the (upper) Cottons should be bulldozed. People may have nostalgia for the houses, but the houses themselves aren't so much the problem, as the chronic lack of available land around them for paddock space. As the Decimus Burton building is listed, there's only one way for the zoo to create an acceptable giraffe enclosure, and thats by expanding over the footprint of the entire upper Cotton's. I am convinced that the giraffe will be gone in under a decade unless this is done. For those who think the megafauna form an essential part of the learning experience for young minds, look at the state of the current enclosure and ask yourselves for how long will people think that's ok?
I agree that grazing is important to both hippo species and, just because an animal lives in tropical forest regions, doesn't mean it's at its most fulfilled being kept on bark chippings on something the size of a small petrol forecourt. London were so keen to create a grassy, forest 'bai' opening for their gorillas, why not for the hippos? Couldn't possibly be because the hippos won't ruin overhead vegetation but will graze heavily, whereas gorillas will do the opposite?
Someone did make a good point about the hippos having grazing access to adjacent enclosures, though. The 2007 masterplan sited the hippo exhibit where the current entrance is; situated here, there is the potential for corridors and channels into the gorilla moat, and perhaps even night grazing on the actual island for some of the year. A much better and economic use of space than reusing a massive ungulate building, designed to rotate multiple species onto minute strips of yard, for just two pygmy hippos. But short-term there certainly exists worse than what they're creating. I would be impressed if they spent a modest amount creating a fenced corridor down to a paddock in the woodland walk, in the way that Whipsnade has done with their pygmy hippo enclosures, but I suspect this won't happen, for various mundane reasons.