‘Let me talk to her. But you’d better not let me down.’

And even though I never make promises, because I am terrible at keeping them, I find myself saying, ‘I won’t let Casey down. I promise you that.’

Harriet gives us a lift to Cheltenham station, which means I have to keep my mouth shut during ten miles’ worth of snarky reminders.

‘. . . and if her sleeping pattern is disrupted, it can affect her immune system, so it’s very important you don’t let her stay up too late.’

I catch Casey’s eye in the rear-view mirror and she’s moving her mouth up and down, imitating Harriet. Her supposed best friend, Molly, had to be press-ganged into taking the journey with us and has been staring at her phone the whole way.

‘Also, remember to use the antibac gel whenever you touch any surfaces that other people might have touched too.’

When we finally board the train, I sigh with relief and Casey laughs. ‘Molly’s mum is a bit full-on, right? But she’s always kind to mine. And to me.’

I want to hug Casey for her fairness and generosity. ‘Fancy sitting in first class?’

‘Won’t they throw us out?’

‘Not if I pay for the upgrade.’

It’s the best twenty quid I’ve ever spent. We get a big table to ourselves, and Casey keeps reclining the seat and straightening it up again, like it’s a fairground ride. The conductor brings us drinks and snack boxes – it surprises me when Casey asks for the kids’ one.

Am I up to this? For all her smart talk and her teasing, she is still a kid: a kid who needs me.

‘I’ve never been in first class before, DL – I love it!’ Casey says.

‘My dad and I always went first-class – until the guard arrived . . .’

‘Did you get caught?’

‘Never,’ I say. Not for that.

Casey and I chat about everything but what has happened with her mum. Whisper about the other passengers in the carriage. Pick the houses we’d buy as the train speeds through the parched countryside.

When the snack boxes are empty, we fall silent. Her eyes dart back and forth as she watches the world whizz by. My eyes. My mum’s eyes. I wonder what kind of a mother she’d have been, how my life would have been different if she’d lived.

‘What was she like?’

Casey’s question startles me. For a second I think she’s talking about my mother, but then I understand she means Angelica.

‘When you met her? What made you like her?’

I close my eyes, trying not to see the bony, exhausted woman we left behind. Taking myself back in time, to a filthy, sodden field and a different me.

‘Well, the first time I saw her, everything stopped. I couldn’t even hear the music.’ I open my eyes and Casey is watching me intently. She needs to know her mum was special. ‘Angelica was dancing in the coffee queue with her friend, wearing a bikini top and denim shorts under a big see-through poncho and flip-flops, mud all up her legs. She was knockout.’