‘Then there’s nothing to worry about. But for now, every detail of the night before is important.’

‘Can you promise you won’t bring her into the investigation, Bish?’

‘I’m not part of the investigation. As far as this case goes, I’m just another father who wants to know who’s behind this thing. I can’t promise something I can’t deliver, but I will promise that if Greta has to be questioned again, I’ll be there with you all.’

Bish waited, then at last heard a sigh.

‘She says that on that night, she saw a security car being pushed out of the grounds. The engine wasn’t on. Or the lights. She knew it was security because of the shape at the top of the car.’

‘Get her to write down everything she saw. Tell her not to leave anything out. I’ll pass it on and we’ll keep her name out of it until we have no choice.’

‘We just don’t want whoever’s responsible for the bomb knowing Greta saw anything. We’re really worried about her. How’s your daughter holding up?’

Bish heard a break in the man’s voice. He couldn’t hang up now, so he chatted a while longer. He then sent a text to Grazier detailing the conversation, and one to Attal as well, even though Bish knew he wasn’t on the case anymore. Then Naomi Hill returned his missed call. Reggie’s mother had met Parker at the Boulogne hospital on that first day, before Reggie was discharged.

‘Are you joking, Bish?’ she said when he asked if she’d had further contact with Ian Parker. ‘Have you read what he says about young black people? It’s not just migrants he goes after.’ She added briskly, ‘Anything else?’

‘Yes. Can you tell me what photobombing means? And how to use Instagram?’

Naomi worked for an entertainment magazine, so he figured she’d know. It was an icebreaker.

‘You need an account for Instagram,’ she said. ‘All your photos go public unless you set your account to private. Then only the people who follow you will be able to see them.’

So he had to continue begging people to be his friends online.

‘Do you think I could follow Reggie’s account?’ he asked.

Within an hour he had access to ten Instagram accounts. He pitied French Intelligence, who had to go through eight busloads of teenage photography. Under any other circumstances Bish would have taken the time to despair at the priorities of the young. Seven days in Normandy and hardly any landscapes or monuments. Who went to Mont Saint-Michel and took selfies in the gift shop?

It was at lunchtime, when he was back on Facebook, that a gift was presented to him. Bish couldn’t help marvelling at his ubiquitous mother. Absent throughout his teenage years, everywhere he turned in his middle age. Saffron had a hundred and thirty-four Facebook friends. Katherine Barrett-Parker was the latest.

After a quick phone call he went to pick up his mother and drive her down to Dover. Earlier that week she’d travelled to Boulogne to visit the injured kids, and had met both Katherine Barrett-Parker and Sadia Bagchi.