And, like the most perfect picture, for a moment everything stands still. The sun is gloriously golden and warm. The birdsong is brighter and sweeter than ever before, the monkeys at their most playful and full of joy.

I try to look unruffled, as if people declare me to be their Best Friend every day. ‘Of course,’ I breathe, and I can’t help smiling. ‘Always and forever.’

We sit for a moment in contented silence.

‘What is it that your father doesn’t like about mine?’

‘Honestly, don’t worry about it.’

‘He shouldn’t say things about people he doesn’t even know.’ How odd to think of Vati being discussed in other people’s living rooms.

Erna takes a breath. ‘Something to do with the way he took over the newspaper,’ she says in a rush. ‘But he’s probably got it all wrong.’

Frau Goldschmidt’s wrinkled crone-face swims into focus. Your father… forced them out… all lies and falsehoods …

Jealousy. That’s what Vati said it was.

‘It’s all lies and gossip. People are jealous of my father’s success, that’s all.’

I meet Erna’s eyes and she looks away.

‘Yes. That must be it.’ She digs a hole in the gravel with the toe of her shoe. ‘My father’s a silly old fool for listening.’

‘He should be more careful.’

The monkeys have eaten most of the fruit and begin a game of chase, swinging from pole to pole. The grooming couple saunter off and disappear into the covered enclosure.

‘I’m going to join the Jungmädel,’ Erna says. ‘Will you come too?’

‘Vati won’t let me. He thinks the HJ should just be for boys.’

‘But everyone else is. Surely you can persuade him?’

‘You don’t know Vati. When he’s made up his mind, it’s impossible to change it.’

Perhaps Erna will find a new Best Friend in the Jungmädel. I scan the flat, green expanse of Rosental stretching out towards the woods in the distance. The sun is suddenly too hot and the glare hurts my eyes. I can feel a headache developing in my temples.

Erna gently touches my arm. Her eyes are stretched wide open.

‘Please don’t tell your father what mine said, will you?’ she whispers.

‘Of course I won’t.’

‘I can trust you, Hetty, can’t I?’

‘Erna,’ I look straight into her cat-like eyes, ‘I’m your best friend. You can trust me to the ends of the earth. I promise you that.’

10 September 1934

‘Did you hear they got rid of Dr Kreitz?’ Erna whispers.

‘When?’

‘Friday. And other teachers too.’

She nods at the solemn-suited wall of authority at the front of the main hall where we are gathered for assembly. There are definitely some new faces amongst them.

‘Quiet!’ Herr Hofmann’s voice booms. ‘Silence for our new science teacher. Herr Metzger, the floor is yours.’

A slim young man in a brown suit and bow tie strides to the front of the stage. His young face is round and shiny and a smattering of white pimples cover the rough, red skin of his chin. He can’t be much older than Karl.