Prove it, John says and Marcus exhales, trying to work out how he might do that. It's not as if he and John have taken a load of selfies together and they're just sitting on his phone waiting to be shown. He could call Kat, he supposes, and she would corroborate his story, but there's no reason for them to believe Kat either.

He knows damn well he can't tell them about their futures. They're children, even if they're really not. Not with what he knows about John, with what he's done, the stories he's given.

In the end, he does the only thing he can think of. He takes out his phone, unlocks it and passes it over. "Go to my contacts," he says. "You'll see yourself in there, John. There's a picture in your contact. Martin, I'm sorry, I don't have your contact, you're not in there."