They found Daniel just inside the marquee, sipping water and patiently receiving congratulations. His beard, grown since his conversion, was neatly squared off and his previously shoulder-length hair was cut above the ears. He smiled at their approach, something he would not have done before. ‘No cloaks or daggers here for you two, I’m afraid. Unless you want to disappear into the rhododendrons.’

Sarah laughed. ‘Might be misconstrued.’

As they elaborated on their congratulations, Charles’s mind returned to his working lunch with Michael Dunton, director general of MI5, earlier that week. He and Michael lunched monthly on sandwiches and fruit juices, alternately in each other’s offices. Charles, being like red-faced Robin of a generation for whom lunchtime drinking had been a sustaining prop for the rest of the day, deferred unprotestingly to the fashion for abstinence while secretly regretting it.

‘One last thing,’ Michael had said. ‘Sarah has a godson, I believe, who is a recent Muslim convert?’ They had dealt with all their other business, the usual run of incipient turf disputes, resource allocations and personnel issues that it was in their mutual interest to resolve before they became too serious.

Charles raised his eyebrows. Any item introduced as ‘one last thing’ was rarely an afterthought. ‘How did you know?’

‘Facebook, apparently. Not that Sarah’s on it, I’m told, but the godson’s mother is and Sarah features on her page. Ditto young Daniel, of course, hence some of his associates, and it’s them we’re interested in. A couple of them, anyway. They’ve been recommending certain extremist websites to him, the sort that encourage self-starters to strike a blow for Allah with knife or vehicle, that kind of thing. No indication that he’s about to oblige but they’re saying that converts need to prove themselves and he doesn’t seem to argue with it. I only mention it because we discovered your connection with him via Sarah via his mother and all the wedding stuff and the desk officer thought you should be aware of it.’

‘He’s quite right. Please thank him.’

‘She also asked whether Sarah would be happy to meet her and talk about Daniel in case anything looks like developing. Assuming Sarah knows him better than you do?’

‘She does, yes. I’m sure she would be happy to meet her.’

‘Thanks. Gareth Horley seems to be behaving himself, I’m happy to report.’