It was a dreadful enclosure, very small with grey concrete and those horrible bars. There was a wire mesh barrier to waist height as well, which you can just see in the photos; it did keep people at a safe distance.
Read Gerald Durrell's "Beasts in My Belfry" for an account of this enclosure and its vanished carnivore pit neighbours.
It was appalling, but the bears did well there; I think ten cubs were reared there in the 1960s and 1970s. Admittedly, it wasn't easy for male and female to avoid coming into contact with each other in an enclosure that size!
If anywhere in England has the space to do Polar Bears properly, it's Whipsnade. I'd love to see them back - done properly this time!
The barriers around this and the Lion and Tiger Dells were all pretty similar-the classic ZSL chainlink. There was at least one accident with the Lions in the 1950's- a young boy(a cub scout?) climbed over- I think he died from the mauling he got.