She was worried he didn’t get enough activity – of course he didn’t, living in a cell – so for the last year or so she had been doing exercises with him. They began with jogging on the spot – he found that amusing – and then they dropped to the floor and did press-ups and sit-ups. Max’s press-ups mainly consisted of him raising his bottom in the air and then collapsing to the floor, but it was something. Maggie had found that, as the months went by, she could do more and more of them; now it was no trouble to do fifty at a stretch. She also did tricep dips and planks; she could hold the plank for over four minutes.

Maggie took off her T-shirt and shorts – it was always uncomfortably hot in the room, the air still and cloying; the only time there was any fresh air was when the man came and cooler air gusted in through the open door – and knelt on the floor. She dropped into the press-up position and did twenty press-ups, then held herself on her elbows.

‘OK, Max,’ she said. ‘Come and join me.’

Max toddled over. He was in a pair of dirty underpants – she tried to keep them clean, but it was hard with only soap and cold water – and lay on his belly next to her. On the back of the underpants was a Superman logo she’d drawn once, after telling him the story of how Superman had come from the planet Krypton to save people on Earth from their own folly. As she recounted the story she had been gripped by a powerful feeling that Superman would burst into the room and rescue them at any moment. He hadn’t, but for days she had been left with a vague sensation of hope.

Max levered himself up into the plank position. He was still some way off a four-minute plank. Once he had managed about twenty seconds, but this time it was closer to four seconds before his buttocks started to quiver with the effort. After a few more seconds his hips slowly lowered to the carpet.

‘Watch, Mummy,’ he said, looking up at her. ‘Watch what I can do.’

He started to wiggle his legs and arms and shake his head from side to side.

‘Wow,’ she said. She paused while she searched for an appropriate description of his gyrations. ‘You’re break-dancing!’

‘No,’ he said. ‘I’m being a snake. A snake doing yoga.’

‘Oh,’ she said. ‘Of course.’ For a while they’d done some stretches she remembered from PE and she’d told him they were doing yoga, and it had obviously stuck with him.

He wiggled around for a while, a look of triumph on his face, then stood up and ran to Maggie. He jumped on her back and pressed his cheek to her skin.

‘OK,’ he said. ‘Ride the horsey!’