We were burned out, and after we’d kissed again we agreed to leave Six. To run away. We joked about hot countries that had no extradition treaties with Britain. I suggested Cameroon, Namibia or Venezuela.

‘Caracas has a thriving literary scene.’

‘And it would be easier to blend in,’ she said.

Neither of us had worked the South American beat. The Caribbean would be our playground: Montserrat, Grenada, St Lucia. I would ignore the drug boats, the private jets from which men emerged with briefcases chained to their wrists, the officials behind high gates. I’d stare out to sea.

We talked about unimaginable things: a home, children, jobs we could admit to. Our lives would be quiet and apolitical. Love would demarcate our cares.

‘We’d need money,’ she said.

Six months ago. I had assumed she was still here. I walked past the place she’d been living, one of a cluster of 1940s suburban semis close to the railway station. The front garden had been mowed, then strewn with plastic toys: a tricycle, a slide for a toddler. A maroon Citroën people carrier occupied the driveway. Through the windows, a woman in an apron was washing up.

I went to the end of the street and bought a pair of gardening gloves from the shop opposite the station, tore the tags off. Then I knocked on the door of her old home.

The aproned woman answered, drying her hands.

‘I live around the corner,’ I said. ‘Borrowed these off the woman here, but a while back.’

‘She’s not here any more.’

‘Oh. When did she move out?’

‘We’ve been here five months.’

‘I don’t suppose you have any forwarding details?’

‘None at all. And nor does the former landlord, apparently.’

Joanna’s parents were in the phone book. I met them once. They were mannered, English. Father ex-City, a wine trader, womaniser; mother discreetly Christian, frail. She liked me. ‘Joanna never brings anyone home,’ her mother said. Joanna’s personality with them was hilarious; all smiles and self-deprecation. The dutiful daughter with her rising career in the civil service. I wish they’d seen her firing an Uzi.

She was protecting them from herself, I realised. Your closest family members don’t have to be completely in the dark about an MI6 career, but you have to ask why you’d give them that to think about. I felt they deserved to know of her coolly walking into a room of Eastern European fascists, enduring enhanced interrogation training, setting up radio stations in the Afghan desert.

‘It’s Elliot,’ I said, when her mother answered.

‘Oh yes. Hello.’

‘I’ve been having difficulty tracking Joanna down. Any idea where she is, or how I could get hold of her?’

‘We’ve no idea. I’ve not heard from her for ages. I thought she was abroad. She never tells me much. Should we worry?’