Afterwards, when he and Sarah were clearing up, he told her of another obsessive he had known, an older man, a dentist, sensitive and artistic, who had been among the first troops into the Belsen concentration camp in 1945. In later life he had made beautiful, suffering miniature figures from his dental materials while becoming obsessed by the world’s population increase. This concern found a way into every conversation until eventually it became impossible to talk to him about anything else. When he killed himself – also using dental materials – he left a note saying he had done it to reduce the world’s population. Charles recalled his own unfeeling youthful reflection that, if that really was his concern, it might have been more rational to murder his daughters.

‘But Daniel’s not as monomaniacal as that,’ said Sarah. ‘He was talking quite normally for most of dinner. Anyway, he seems too keen on it all to kill himself– it’s a sin in Islam as in Christianity, isn’t it? Unless you seek martyrdom in battle while defending the cause.’

‘He thinks terrorists are martyrs.’

‘But that’s almost conventional, isn’t it?’

‘Among extremists.’

‘He doesn’t seem that extreme to me, no more than Christians who believe in creation myths or transubstantiation. I don’t get the impression he’s going to set about non-believers with his hammer and chisel, do you?’

‘Except that what he espouses amounts to a call to action rather than a statement of faith.’

‘It’s just the enthusiasm of the convert, if you ask me.’

‘Obsessives are wearisome, all of them. They’re not all mad but I think he’s going that way.’

‘I don’t. I think he knows a hawk from a handsaw.’

‘Do you?’

He arranged the session with Gareth for seven the following evening, not late enough to be out of the ordinary but a time by which most people would have gone home. They would be alone. He had told his secretary – he still thought of her as that rather than as his EA, executive assistant, as secretaries were now styled – to tell Gareth’s EA that it was to discuss a development strategy for Timber Wolf reporting. Gareth liked discussing such concepts and would not, Charles hoped, arrive in defensive mode.