It's a pity that the Bongo and the Red River Hogs are at Whipsnade.
Both species would complement the 'forest-dwelling' Okapi and Pygmy Hippo at London nicely. However with the enlarged paddocks the Okapi and Hippos now occupy, I'm not sure where the Bongo could go- unless the Zebra were to be replaced. They(the Zebra) do look a bit miserable with no grazing- just standing about. Whereas Bongo being browsers would be more suitable for those urban-style paddocks. But I suppose people expect to see Zebras and 'antelope' are lower on the list of 'want to sees'.
Unfortunately I doubt anybody misses the Red River Hogs at London- they have the more popularised Warthogs to look at and one pig species there is probably sufficient. I noticed the Hunting Dog enclosure has been extended to encompass what was the RR Hogs area.