Of course they would act, if it was an assault. An assault was different. An assault was more serious than someone drawing obscene graffiti: everyone knew that, so what was the point of the comparison? Why had Michael thought, even for a moment, that a room full of Transport Police might want to sit studying the footage, hunting for images of Ejay as he or she fled the station with the marker pen in his or her hand? What would they do if they identified him – because it must have been a boy, surely? Would he be arrested and made to pay?

‘You’ll have to pay, I’m afraid,’ said a smooth voice in Michael’s head – sing-song, smiling, with glittering, fun-filled eyes. The smell of the pen had taken him straight back to the classroom, and there was the teacher’s voice.

‘I didn’t know homework was due, sir.’

‘Ah, but ignorance is no plea,’ said Mr Trace as the other boys laughed. ‘Come out here and pay the price!’

‘Wouldn’t they?’ said Michael.

He was speaking to Stefan, who was still at his computer console, listening professionally and not interrupting. ‘You have the CCTV footage,’ he said. ‘So I think something ought to be done. You ought to prosecute these people, because it’s a crime. It’s disgusting.’

Stefan did speak, then. He urged Michael to put his thoughts in writing, and send them to the company so as to open a proper complaint file that would receive further attention. He would need to document the case and detail the exact time and date of the incident.

‘I haven’t got the time,’ said Michael – which was a lie.

Stefan said nothing to that.

I just want the world to be a nicer place, he thought, but did not say. I want it to be better and more decent, and I want… it’s more than that, Stefan. I want big corporations like your train company to spend some of their profits on making our world less foul. I want Ejay to be confronted and helped. I don’t want him fined or thrashed. He’s only a boy and I want him supported, because you can’t go through life drawing ejaculating penises on tables: it’s not right.

Michael said, ‘I don’t have the time,’ and he’d said it in a voice that suggested that even this call now had to be hurried. Perhaps Stefan was imagining Michael just as Michael had been imagining Stefan? – in which case perhaps Stefan had an image of a forceful person, neatly dressed and professional, sitting amongst files and invoices, his laptop chirping softly as the emails landed. The Michael that Stefan saw was a conscientious traveller who’d made the time to follow up on an experience that had disturbed his sense of propriety, but now – duty done – he had to return to the pressures of his demanding job and loving, needy family.