She could remember their compartment as if it had been a few weeks ago. The cooked-vegetable smell that wafted in early evening from the dining carriage, the flimsy curtains that she pulled across every night – except for one particularly clear night, halfway through their trip, when they’d kept the curtains open to watch the stars through their small square window. There were bunk beds that they were supposed to sleep in, each one barely big enough for a person – he’d confined himself to the lower bunk when they’d argued at the start of the trip. But eventually they’d climbed into the top bunk together, enjoying the closeness, laughing at the fun of it, clinging on to each other so as not to fall out during the night.

‘It must be possible to sleep like this. Humans used to live in trees,’ Piotr had said, his voice softly close, his breath sleepy-stale and familiar.

‘No, that was caves,’ she’d replied. ‘You’re so confused, sweetheart. Must be the sleep deprivation.’

‘I mean before the caves, sweet potato.’

The train’s wheels had clanked over some uneven track, both of them opening their eyes wide in alarm. ‘Sounds a bit wild out there,’ he’d whispered. But the train had carried on.

‘So, you mean back when we were monkeys?’

‘Apes.’

‘Then tell me, how did we balance on the branches?’

‘By wrapping ourselves all around them, like so.’

‘I see,’ she’d laughed quietly, into his chest.

‘That’s why we have such long arms and legs.’

He’d curled his legs around hers and pulled himself in closer.

‘So, I’m like the branch here?’

‘Skin smooth as eucalyptus.’

‘And that would make you a koala bear?’

‘Still an ape.’

‘Well, you’re hairy enough for it, I suppose.’

‘And there I was being so charming.’

Eva closed her eyes and allowed herself to fall back into the memory, just for a moment. She wished the trains into London juddered on the tracks the way the old Trans-Siberian trains did. She wanted to be jolted, to feel the movement of travel while she was travelling. All this gliding was too easy, made you forget the miles that were passing below your feet. It was like the colour green, everything painted green to be relaxing. Where did it come from, this obsession with everything being perfect? She wanted the rough edges back.

The endless birch trees, she remembered, bark shimmering in and out of the winter sunlight as they sped past. She hadn’t realised that was what it would be like. When she’d thought of Siberia, she hadn’t pictured birch trees – she’d imagined it as desolate and windswept. But then they’d passed Irkutsk and followed the shoreline of Lake Baikal, and there were no more trees. It was flat and desolate, the expanse of water reflecting the globe of the sun.