‘It’s partly that, yes, along with the fact that the other people in this mosque he’s started going to get very excited every time there’s a terrorist knife attack anywhere. They get all the details about it and analyse them and talk about how to do it better. Plus the fact that his wife is worried, as you reported.’

‘So it’s not just partly the knives, it is mainly the knives?’

‘They’re a large part of it, yes. But there’s also this.’

She produced a small laptop from the briefcase she carried and inserted a memory stick. ‘This is what the DG asked if you could come over and listen to. It’s a phone conversation between Daniel and one of his mosque friends. We’d like to know whether you have any idea what it refers to. It could be knives but we’re not sure.’

They listened three times to the short dialogue. A man who sounded of Indian-subcontinent origin rang Daniel and asked, without any preliminaries, if he had got ‘it’. Daniel said yes, it looked good. The man asked if it was somewhere safe and Daniel said it was. The man said, ‘See you on Friday,’ and rang off.

‘We’re not sure what they’re talking about,’ said Shelley. ‘Do you think it could be a knife?’

‘Doesn’t sound like it. It’s a bit odd to say it looks good. A knife is a knife, pretty simple thing. And he’s got more than one, of course.’

‘Maybe he means it’s fit for purpose, whatever that is.’

‘Maybe. There’s also the implication that he’s hidden it. But we know his wife knows about the knives and anyway why would you hide a knife when you can just keep it in the kitchen drawer with others? Unless it’s a special knife for hunting or skinning or something.’

‘That’s really why we want to get in there, to have a look and see whether there’s anything else suspicious like guns or explosives or chemicals. Any signs of preparations for violence.’

Charles was still reluctant to imagine Daniel as a terrorist and unconvinced that he merited this level of investigation. But such assessments were MI5’s business, not his. ‘It’s a pity we didn’t know about this when we had them round for dinner. You could have done it then.’

Her nervous smile reappeared. ‘Perhaps – we did wonder whether it would be possible for you to ask Daniel to come and look at doing some carpentering work on your house for you? Then we’d know where he’d be and for how long.’

‘I suppose we could, yes.’ He was wondering what Sarah would think of that. She had said something about rain coming under the back door when the wind was in that direction, which he had failed to notice.