It was a cold, overcast day. I had forgotten the smell of zoos, the distinctive earthy whiff of llama urine and zebra shit wafting over from the pens. I bought Raymond a shiny souvenir map from the shop and gave it to him, telling him it was his job to direct us around the animals. He took his task seriously, squinting diligently at the pathways on the map. He wanted to start with the camels, and we walked over to where they were chewing sideways and sulkily, their drooping mouths trailing strands of hay. Their coats looked mangy and their humps had slumped to one side like deflated bags.

‘They like to run in the sand,’ said Raymond. ‘That’s why they’re grumpy here.’ He knew these things from the animal encyclopaedia Eve had bought him a month ago: I had seen him looking at it with a rapt face and open mouth.

Then we went to the gorilla enclosure. The massive silverback, the daddy of the troop, rose up on his enormous haunches and ambled towards us. Raymond reached for my hand. We stared at the gorilla. The little jewelled eyes set in his great, seamed mask stared back at us, impassive and dignified. He turned round, presenting the vast expanse of his silvery behind, and walked over to a darkened corner, where he sat in profile, eating a banana. His gigantic hands worked with a clever delicacy, peeling off the yellow skin. It was like watching a very fat man dance on nimble feet.

‘He doesn’t have enough space in there,’ Raymond said. ‘He should have more trees and things to swing from.’

He was right, of course, but I didn’t want Raymond walking from enclosure to enclosure feeling sad for the animals cooped up inside. I could sense the dust of gloom settling on our outing. So I steered him instead towards the creatures that have the gift of appearing content anywhere, even Regent’s Park on a grey November day: the frantic parakeets and the capering spider monkeys; the lazy, ornamented iguanas and the big-eyed lemurs that darted and scuttled through underground cages in an artificial half-light. He liked all that, and he started to laugh and chatter about the way they looked and point things out about their strange hands or curious toes.