Six years of work, I thought. This was meant to be the one that went well, that meant I could retire with my head held high, even if no one knew anything about what I’d done. The absurd image that wouldn’t go away involved somewhere homely, where I was talking to a child, possibly my grandchild. He held a yellowed clipping while I said something like: I played a part in this. This is who I was, even if you won’t read about me anywhere, except between the lines. In this old shoebox is an MBE. No, I don’t feel any need to display it. The Queen leaned close to my ear and said she understood I had contributed a huge amount behind the scenes.

‘I’m moving on,’ I said. ‘Leaving Six.’

‘To what?’

‘I have notes for a book: the poetry of Islamic Spain, the invention of love. I want to retrace the steps of the troubadours, lose myself somewhere foreign that I don’t have to spy on.’

But as I said it I realised, with a chilling clarity, that I wasn’t leaving anything without Joanna. Certainly not with her missing. Stevenson checked his watch, wrapped the leash around his hand.

‘Listen, Elliot, I should go. Sunil will be wondering where I am. But will you keep in touch? And not do anything reckless, for anyone’s sake?’

‘Of course.’

‘You’ve been through a lot. I know it’s all a day’s work for you, but you deserve a break.’

‘Can you sniff around?’ I said. ‘Keep an ear open?’

‘They don’t close any more.’

He placed a hand on my shoulder then returned towards the streetlights. I watched for other silhouettes but none came. I stayed on the bench, enjoying the darkness and the sensation of being alone.

AWOL. Where would she go? She was impulsive, a thrill seeker. Given how ill-advised our relationship was, it’s a wonder she hadn’t initiated it sooner. But I had always thought there was an unspoken agreement, an understanding that this final step would destroy us. We found alternative kicks. We would slip into improvisations while out, snap covers, games we’d developed during training; introduce one another by names made up on the spot, choose ridiculous environments to penetrate: a meeting of Quakers, a protest against undercover police, a far-right march.

‘It will be interesting,’ Joanna said, pulling me into the thin flow of marchers, adjusting her hair, her voice, ending up three hours later almost being glassed by a coked-up skinhead in East Ham. All of which was exhilarating and made you feel like you were both special, and deferred the awkward honesty of a relationship.