It came from the boy ahead of me: a boy with outlandishly long hair, curling about his ears and down his neck and almost to his shoulders. I had never seen a boy with such long hair before. His mother looked strange too: she wore a yellow bead necklace that rested oddly on large, drooping bosoms under a roll-neck jumper.

‘Mummy,’ said the long-haired boy. ‘How many Rhesus monkeys again?’

The mother shifted her hips and looked for something in her handbag. ‘Oh, about 10,000.’

‘And they all died? Every one of them?’

‘Yes, darling. Or perhaps they were paralysed, I’m not sure. I can’t remember exactly.’ She pulled out a tissue and blew her nose. Her handbag had a leather tongue on it and a tribal face.

The boy was quiet and thoughtful. ‘It must be awful for a monkey to be paralysed,’ he said. ‘They couldn’t swing around or anything!’

‘It must be awful for a little boy to be paralysed,’ said the mother. ‘Though it’s sad for the monkey, that’s true, darling.’

I nudged you. ‘What are they talking about?’ I pointed to the mother and son in front of us.

‘What?’ you said.

‘Monkeys being paralysed.’

You looked momentarily befuddled and slightly cross.

‘Ree-zus monkeys,’ I said. ‘Getting paralysed.’

‘Oh,’ you said. ‘Yes, they did experiments on monkeys, Owen, to make the vaccine. That’s what they’re talking about. They had to experiment with the injection before they tried it on humans. You know, to make sure it was safe.’

‘Experiments on monkeys …?’ I said.

‘Yes. The scientists experimented on the monkeys and that’s how they come up with the polio vaccine. No monkeys, no vaccine.’ I must’ve looked appalled then, because you said: ‘What? You think a monkey is more important than a human being, Owen?’

‘No,’ I said. ‘I just don’t think it’s fair to the monkeys.’

‘Look Owen.’ You were putting on your hospital voice, which I always took to mean ‘end of conversation’. (It often coincided with you looking at your watch.) ‘My cousin Frank, right, he got polio when he was seven. 1952. Had to go in an iron lung for months. Never walked again. Never got to run and jump like you and grow strong bones. Has to go in a wheelchair now. You want that to happen to other kids, maybe to you?’

‘No.’

You must’ve heard my lack of conviction, because you sighed and pretended to be patient. ‘If they don’t experiment on animals, Owen, human beings gonna keep dying of things. Those monkeys give their lives for a good reason. You want little kids to grow up crippled?’

‘No,’ I said again. I felt very glum. We were getting right close to the front of the line now. The curtains on the cubicle were open and I could see a white plastic spoon going into the mouth of a little blonde girl. Now it was the boy with long hair’s turn. Despite his previous questions, he didn’t seem fussed. He marched forward and opened his mouth like he was getting a lolly.