I'd agree with the part about all the extra requirements for Polar Bears making them much more expensive to maintain in captivity properly, than other bears. But virtually all the larger UK Zoos used to exhibit Polar Bears in the 1950's/60's, at one or two (like Chessington & Bristol), Polar Bears were the LAST species to go. Also several provincial zoos in the UK have bred Polar bears, some quite successfully too, though they never made the headlines in the the same way as London Zoo's used to. That's just a bit of zoo history for you- today only one Uk zoo still has one, an old female(Mercedes) at Edinburgh. Due to the usual critisism they weren't going to replace her when she died, but are now talking about a major new Arctic exhibit with possibly..... Polar Bears.