Hazel Fletcher gave him a wry smile. ‘I’ve worked with children for almost thirty years, Detective Winkler. I don’t shock easily.’

‘Do you have internet access on that computer?’ he asked. ‘And do you have a firewall that prevents access to adult material?’

She did. Winkler waited while a guy with a head that was balder than a baboon’s bum fiddled with the settings on Hazel’s computer. After Baldy had left, Winkler read out the URL of the porn clip, then sat back while the head teacher watched it. Her face gave nothing away. He wondered idly if she was slightly turned on by it. She’d never admit it, and neither would he, but when it came down to it humans were animals. The whole lot of them were only a few social niceties away from tearing off their clothes and cluster-fucking in the streets.

Winkler told Hazel what he knew about the source of the video. ‘And Alice Philips and Larry Gould are currently whereabouts unknown.’

He expected her to start spouting off about how Alice and Larry were model pupils and how she couldn’t possibly imagine how they could have done such a dreadful thing. But he guessed she hadn’t been exaggerating when she’d said she’d seen it all.

‘So you think Alice and Larry made this video with some other . . . children from this school.’ She grimaced at the world ‘children’.

‘We don’t know that for certain, Mrs Fletcher.’

‘Ms Fletcher.’

Of course she was. ‘Sorry. I was always getting into trouble with the headmistress when I was at school.’ Tumbleweed rolled in the space between his sentences. ‘I need to find out everything I can about this video and who knows about it.’

‘Is it a criminal offence, what Alice and Larry appear to have done?’

‘It depends. If the kids in this video are under sixteen, it becomes a lot more serious.’

She nodded grimly and picked up her phone. ‘Sarah, can you get Danny Clarke in here? Yes, I saw him earlier. He’s here today. For a change.’ She put the phone down and addressed Winkler. ‘If anyone knows about this, it’s Danny Clarke. He knows everything that goes on at this school.’

Shortly afterwards, the receptionist escorted a five-foot-nothing boy with a fringe that flopped over his eyes into the office. Winkler had been expecting a member of staff, not a kid. But Danny Clarke was, as Hazel now explained, a Year Ten student. Winkler almost laughed. It appeared that the head teacher used Danny as the equivalent of a police informant. Danny sat down and his leg immediately started to jerk up and down; he had the worst case of restless leg syndrome Winkler had ever seen. His leg gave off enough kinetic energy to power a small town for a week.

Hazel fixed Danny with a serious look. ‘Danny, this is Detective Inspector Adrian Winkler.’

Danny sniggered.