‘Wrong side of town, it seems. Total cock-up; no one’s pretending otherwise. We think perhaps the Turks stuck an oar in. Washington’s got its new tunes, as you know, and that’s causing pressure. Things were going to come to a head sooner or later.’

Fieldwork sometimes felt like being told to build elaborate and very fragile constructions next to the sea; one day the tide of diplomacy turns and you wonder why you bothered.

‘We appreciate the work you’ve put in,’ Mitchell said.

‘We’re all frustrated,’ Undercroft elaborated. ‘But those theatres aren’t the priority they once were. And there’s an additional problem.’

The problem was $500 million worth of weapons supplied to Yemen’s interior ministry which had gone astray. The Foreign Office had got jumpy and instructed us to cut all ties before taxpayers’ assault rifles turned up on jihadi YouTube. They were very concerned about what ‘bore our fingerprints’.

So that was that.

Christopher Bohren had two homes I had decorated, friends, prospects, magazine subscriptions. Obviously, some of this would linger. His work would be reabsorbed by the legitimate art dealership housing him; his personal contacts had been primed for an unannounced departure. Operations Security would fade him out of existence over six or seven months. But it would not be me any more.

When we’d exhausted our thoughts about the events of the last twenty-four hours they brought out lists of names. Mitchell had the air of a man who was about to deal with men even less patient than himself. He wanted me to treat former contacts ‘unsentimentally’ in order to ‘clarify the situation’. It was a phrase the Russians used to mean ‘kill someone’.

Every deal I’d made had been cleared with the FCO, yet they had a way of asking about it as if I’d sat alone in the desert wondering how to equip the Free Syrian Army. I existed because of the things the government wasn’t allowed to do, and that brought vulnerability. I began to think through the individuals who might have been here but weren’t, and what their absence signified.

I cooperated with Mitchell’s questioning, but you learned to give London what it needed and not much more. The Foreign Office cannot bear too much reality. When you travel between a world of reports and the one that people die in, intelligence product becomes a dubious thing. You impose order on chaos, give other people a false sense of understanding and authority. It involves the transformation of friends and brothers into agents or targets. That was the border crossing that eventually exhausted you. I wasn’t prepared to endanger someone who’d recently had my back just because of a policy change in Whitehall.