At least Wendy was walked through the grounds. I've no idea if all their elephants were exercised in this way. She was notoriously tempermental, even objecting to the arrival of a new okapi in a nearby enclosure a few years back.
The previous Asian Elephant at Bristol was Rosie, she gave rides throughout her adult life, her main (only?) form of outside exercise as the elephant house had no paddock then.
Wendy & her African companion Christina were walked in the grounds(almost) daily until they were quite large. After Christina died I don't ever remember seeing Wendy exercised alone and I think they had stopped taking them out anyway.
I think the last elephant kept with Wendy for a short while(a few months) was 'Mya' who is now at Chester. However Bristol said that SHE bullied Wendy(not vice versa) which is why they moved her out again.