‘So what do you want to know?’ Gemma asks as we walk along the corridor. The dog trots happily into the lift and wags his tail when the door opens again.

I think about what Mum would ask. ‘How can you be sure it’s safe for people like me? Aren’t dogs home to, like, billions of bacteria?’

The staff wave at Bear as we pass reception and, in the courtyard, a patient comes to fuss over Bear before Gemma can even answer me.

‘We’re all home to billions of bacteria,’ she says. ‘Most of them we get along with fine. And sure, Bear walks on dirty pavements, but so do we, and we don’t make everyone wash the bottom of their shoes before they come into the hospital.’

‘That’s different. We don’t touch our shoes very often. But people stroke dogs all the time.’

Gemma nods. ‘You’re very smart, aren’t you? I use antibacterial wipes before and after Bear comes here. Because it works the other way too. Bear might pick up something on his paws while he’s inside the hospital?’

I get out the exercise book where I’m going to write notes. ‘OK, normal people might be safe around dogs. But my immune system is rubbish, and I catch colds all the time. I could catch something worse from him.’

The dog’s lying on a paving slab now, but with his head on her sandal, like it’s a pillow. He doesn’t look dangerous. He looks cute enough to be on Instagram.

‘I always check in with Mr Porter or the doctors, in case there’s a patient who might be at risk. So the fact that I’m allowed contact with you means the medical teams don’t think you’re vulnerable right now.’

‘My mum says I am.’

Gemma nods. ‘It’s natural for mums to worry. But there’s evidence that people who spend time around dogs may have stronger immune systems.’

‘How come?’

‘I’m not a scientist, I’m an artist, but I think it’s because our bodies get small doses of different germs which makes us better at spotting and fighting the dodgy ones.’

Of course she’s totally an artist! The dress she’s wearing has bright flowers on it, and her toenails are painted different colours, like a rainbow. ‘What kind of art? Are you like Banksy?’

‘Not quite. I draw things for websites and magazines.’

‘So why do you come here? Do you get paid?’

‘No. But Bear likes people and he likes to be busy. He’s a terrier. They were bred to work and if he gets bored, he’s a monster. So volunteering is good for him.’

‘I don’t think I’d come to a hospital every week if I didn’t have to.’

Gemma gazes past me, up at the atom sculpture above our heads. ‘My husband was a patient here and I know how much it helps to have normal things to distract you, whether that’s a nice cup of coffee or the chance to stroke a dog.’

I should write that down for my article, but instead I ask, ‘Your husband. Does he come sometimes as well?’