The first-drive through Safari Park outside of Africa, and in my very limited experience, the best. In fact, thinking about it, the only other one I've been to is Windsor, and that closed many years ago. Still that doesn't stop it being a great day out.
The highlight for me was the wolves; the lions still look like big cuddly pussy cats even though you know they are not, but the wolves were definitely dogs with attitude. The deer were great too, they come right up to the car and poke their heads in. Unfortunately the elephants have had to move on, otherwise they'd be in the running too.
Check the Longleat website for opening times etc.