Later, lying awake in the dark, Nasim turned the decision over in her mind. The prospect of walking away from her brain-mapping work was wrenching, but it wasn’t as if she was trashing her files and erasing herself from history. She’d already made some contributions to the field, and other people would build on them. She didn’t have to chain herself to one project for the rest of her life just to keep the time she’d spent on it from being wasted.

She had always wanted to return to Iran. Now that her country was finally being reborn, she had to grab the chance to witness that with her own eyes, instead of watching everything unfold from a distance. All the frustration she’d felt at not being part of the uprising would be assuaged if she could at least be a part of the rebuilding.

She began drifting towards sleep. Her mind was still in turmoil, but she was going to have to get used to that. Going back would not be easy, but this was her time, this was her chance to reclaim the life that had been stolen from her. Going back would not be easy, but she knew now that she could not stay away.

It was the day for Javeed to register for school, a week before classes began. Martin drove Mahnoosh to the shop early and the three of them sat in the back room unpacking boxes. Just the smell of new books always made Martin feel refreshed and optimistic; Mahnoosh was less romantic, and suggested that this was all down to traces of glue. Javeed’s task was to crush the biofoam packing chips by hammering them relentlessly with his fists, and to complain at length about shipments that were cushioned with shredded newsprint or plastic bags full of air.

When it was time to leave, Javeed embraced his mother tightly, clinging for a few moments longer than usual. ‘Azizam, azizam,’ she murmured reassuringly, pressing her face against his hair. ‘Don’t worry, you’ll love school.’

‘I know,’ Javeed replied cheerfully.

Martin kissed her. ‘See you this afternoon.’

There was a long queue at the school; they had to fill in a form and then wait to have it processed. Martin didn’t understand why they couldn’t have done the whole thing online; he’d renewed his driver’s licence a month before without leaving home, thanks to a seamless process involving facial biometrics and a gadget that read the RFID tag in the card. Still, it was good for his son to see the school from the inside at least once before starting classes. When Javeed needed to use the toilet the woman ahead of them offered to keep their place in the queue, but Martin sent him on the small adventure of getting there and back by himself.

In the office, an administrative assistant sighted their collection of identifying documents and perused the registration form, ready to pass it through a scanner.

‘I’m sorry, Mr Seymour,’ she said, ‘you haven’t written anything for the child’s religion.’ She raised her pen, ready to correct this omission.

‘He has no religion,’ Martin replied. ‘If the computer won’t accept a blank, you’ll have to write “atheist”.’ He saw a flicker of panic cross her face, but she recovered her composure rapidly.

‘Forgive me,’ she said, ‘but I think you misunderstood the question. What it means is the religion of his paternal grandfather…’ She gave Martin a frank, appraising look, then decided it was definitely worth adding, ‘or great-grandfather, or so on, as far back as necessary.’

‘Are you sure about that?’ Martin had no wish to blow the matter out of proportion, but it would be good to know whether there was an official policy defining atheists out of existence, or whether he was just facing a flustered individual who didn’t know how to handle this minor anomaly.

‘When we ask if children are Kurdish or Arabs,’ the woman replied, ‘the fact is, they are all Iranians, and we simply mean the ethnic group of their ancestors. So it is completely logical and consistent to apply the same reasoning to the question of religion.’

Martin had to admire the ingenuity of her argument. Most likely this woman had no discretion in the matter and she was simply trying to spare them all from the bureaucratic hell that would arise if the computer rejected their registration.

‘My son’s paternal ancestors were Christian,’ Martin conceded. The woman looked relieved and recorded his answer on the form.

‘Which denomination?’ she asked.

Martin honestly had no idea. ‘The Church of Saint Coltrane,’ he said. The woman started writing; when she paused halfway through he added helpfully, ‘Kaf, vav, lam-’ She looked up. ‘I know how to spell Coltrane. I was just wondering whether you meant John or Robbie.’

As they walked away from the office across a small playground, Javeed asked, ‘Why did you make that lady angry?’

‘I don’t think she was angry,’ Martin replied. ‘We just had to decide the right thing to put on the form.’

Javeed looked sceptical, but he let it drop. ‘Where’s my grandfather?’

‘My father died before you were born. And my mother too.’ Javeed flinched a little; Martin had told him this many times, but it was starting to cut a little deeper. ‘They had very happy lives, so you shouldn’t be sad for them.’

‘What about Mama’s father?’

Martin steeled himself. ‘He’s still alive. He’s living in Tehran.’ Again, this was old news, but each repetition carried new weight.

‘So why don’t we visit him?’

‘Because he’s angry with Mama.’

Javeed pulled a face, part incredulous, part anxious. ‘Still?’

‘Yes.’

‘And her mama? She’s still angry too?’

‘Yes.’ That seemed to sting even more. Martin put a hand on Javeed’s shoulder. ‘I know, it’s hard not to be sad about that, but Mama’s very brave about it, so we should be too.’

Javeed turned to Martin, suddenly tearful. ‘If you get angry with me, will you leave me alone?’

‘Ooh, ooh, ooh.’ Martin lifted him up and held him in his arms. ‘That’s never going to happen. Never ever.’ Martin carried him all the way to the car, ignoring the growing twinges in his back. ‘Come on, no more crying. Remember what I promised you today? We’re going to Uncle Omar’s shop.’

Javeed recovered instantly, all thoughts of abandonment forgotten.

As they walked from the car together Javeed tried to break free and run ahead, but Martin kept an iron grip on his hand. Ahead of them, three motorbike riders were pushing their way through the pedestrian throng, and though they never had a chance to build up much speed they were easily arrogant and inattentive enough to knock over a small child. As they passed, forcing Martin aside and almost into the gutter, he drew Javeed close to him and resisted the urge to stick his elbow into the face of the nearest rider.

Once the shop door had closed behind them he relaxed, and Javeed ran to embrace Omar gleefully. Then Omar’s son Farshid started wrestling with him, lifting him over his head and turning him upside down. Javeed screamed with delight.

Martin greeted Omar. ‘Javeed just registered for school,’ he explained.

‘Ah, so you’re a big man now? Big scholar? Big sportsman?’ Omar threw some punches at Javeed’s upside-down torso; Javeed flailed back at him, emitting strange martial arts noises from one of his computer games. Omar turned back to Martin. ‘How’s business, Martin jan?’

‘Not bad. You know Iranians; they’re never going to stop buying books. How’s the shop?’ Martin could only see half-a-dozen customers browsing the aisles, but whenever he’d been here at lunchtime the place was packed.

Omar gestured proudly at a new display of cyber-ketabha: two-hundred-sheet e-paper bundles with the look and feel of paper-backs. Each device could store a million volumes’ worth of text. ‘I already sold sixty of these this month.’ He beamed. ‘You’re right, Iranians love books.’